Genetics

Mortimer's family are on his lot, in their graves, and you can see them in his family tree in his profile. If you were to manage the dead, or befriend their ghosts, and/or find a way to resurrect them, you could have a closer look at their faces and see if he might be a product of them with the relationships changed to his 'parents' or the genes skipped a generation. There was speculation once upon a time, that he is the son of Agnes Crumplebottom.

@mw1525 Have you ever gender switched Cornelia? If you had, you would see there is absolutely no resemblance to Morty. I stand by my theory that premade family members are made individually with no use of the parents' genetics. The Bunches are a good example of this. I doubt there is a shared feature amongst the lot of them.
From my memory of "back in the day", my game only gave me zero slider sims as offspring to single parents.

@DivinylsFan Even if he were the offspring of Agnes, I cannot see any shared genetics. I haven't looked at any of the ghosts in his family tree but would be surprised if there were any likeness. Believe me, I have looked at all SV residents as both genders and have a good eye for family resemblance, both in-game and in real life. My son, jokingly I hope, calls me an eugenicist :p

@Mikezumi - No, I have never gender swapped or switched anyone. I take them as they come as exteriors are superficial and changable things to me which, in my humble opinion, has no importantance in what truly makes a sim who or what they are. That being stated, to my untrained eye, Mortimer resembles his mother despite their numerical values being different.

The 'Back in the Day' I was making reference to was in the vanilla base game timeline. The infants of that era all resembled the parent whom they were given to. I currently have a good number of them actively scattered throughout my various worlds. When these sims are toddlers, at first glance you can immediately see which families they were 'born' into as they all heavily resemble their single parent. However, as they become older, they develop into their own form as neither zero sliders nor clones of their parent. They are their own sim; this is how I would imagine Mortimers origin to be.

Apparently the growing up into a different looking face than as a child or toddler was some sort of glitch, which I assume because there is an option in the nraas mod addressing it.
I don't think Mortimer looks like Cornelia. Agnes does have an odd face, as does Morty. Cornelia's is more generic. I hate the hairdo the game gives her when she grows old.
I'm not sure if 'Manage the Dead' was an option without nraas or not, or if the ghosts were more active in the vanilla game, but the gravestones in Mortimer's backyard are of his ancestors. I think there might be one or two in the town cemetery too. Whoever's picture is in Mortimer's, Cornelia's and Gunther's family trees, are a ghost available in the game fabric that can and will eventually come out, and be scrutinised for resemblances. Because they are there, that makes me think that family had to have been played. I've moved a family to another town before without and then again with their deceased's gravestone in their inventory, then placed in their backyard. When they moved without it, their dead relatives didn't show up in their family tree, when they took it with them they did and the ghosts eventually came out and had relationship icons in their interface such as green and orange little people icons for father or mother, grandfather etc. And only the one's who they brought, and I'm pretty sure they needed any generation in between too. I suppose developers and creators could make whatever family tie and ghost they wanted but it seems like it would be more work and mucking around than just playing them.
The mindset and work ways of the people who created and managed Sims 2, who then moved into working on Sims 3, I think would have been to play them and create semi-genuine lore. Today the practices and thinking would be to just create it, and that's apparent with how quickly things move along in comparison. And I think the game and its characters were somewhat more precious to them back then.

NRaas Story Progression has expanded genetic options including getting facial features from grandparents. So if you saw it in someone's else's legacy it's probably from that mod. But it's a big mod to use for just that purpose of course.

@DivinylsFan - The children of single parent sims who grew up to look as neither zero slider sims nor exact clones of their parent were not glitches, they were created as the game developers intended. The base game shipped with the 'genetics feature' already built into CAS it was not an updated add on feature. This feature had to be tested and assigned an in-game role beyond (if) the player would ever use it. Thus, the single parent infants are proof of its presence inside of an ongoing game. However, later in an update EA turned off giving infants to single parents so the genetic feature is no longer used in that way.

But a single parent only accounts for a portion of that sim's genetics. No one really knows how the game decides to fill in the missing genetic pieces of the non-existent parent. It is assumed the game pulls from a single source from the opposite gender but in truth it can pull from many sources as it chooses which may explain why those type of sims always grows up to develop their own unique look.

As far as Mortimer is concerned, which of his parents or neither of them he visually (not numerically) looks like is based on what you see in those sims. In my game, teen Mortimer (not all Mortimers) resembles his mother. This version of him is the one I have seen the most because he is always hanging out in my sim's home. In other games, Mortimer is a very chunky sim who looks like neither of his parents. And still, in other games his face is thin and his expression a bit forlorn closer to Agnes' than his parents.

Yes, the developers of the sims did in fact, play with some of them as they were developing them. Not in the way that 'we as players' play with them but rather as tester sims for all sort of programming and animation checks and a few of those sims actually made it into game with memories in tact. Some even have histories or backstories which were later removed or altered.

@mw1525 thanks. I think it was one of the other two discussing about the single parent situation though. I was interested in whether the facial features skip a generation, or where I'd seen or heard of it, whether in this game iteration or in a mod.
One of my observations was about deceased generations who if their portrait is not in the family tree, they won't come out as a ghost or exist as a relative in the relationship panel. And if moving to another town, if they have the gravestone with them as well as the one's in between they will. Did I wonder if the genetics would be 'remembered' without it, or a memory of a living relative in the old town, I don't know. I do now. I think I remember seeing hair and eye colour operate like that regardless. I say remember because I'm still getting around to setting up a new Christmas break's worth of playing yet.
Its really good to hear there is history and they had been played. Why wouldn't they be eh, too much fun to be had to not.
My understanding is mods aren't created as brand new, but tweaked and modified off of existing game elements, large or small. So having seen things in nraas that play with the chances of grandparent's genetics and facial blending, as well as the thing that addresses the glitch - or maybe its not a glitch but intended! anyway, the thing where when the kid grows up they get a different face, or more or less blending or default or something ... anyway, that tells me that there is something in the game large or small, complex or not, that does facilitate facial features, as well as the obvious hair colours, skipping generations in a dominant/recessive manner, even though in CAS one founding sim might have been created with many tweaks to that feature to make it so original, and I guessed that it must assign the nose, chin whatever to one of the presets closest to it, to be able to then transport it through the genes as dominant or recessive. Perhaps customised one's get higher scores.

There's a neener, neener in there somewhere. Whomever fancies there is.

@DivinylsFan - This is the first time I have ever heard of sims getting a new face. I haven't personally witnessed that; it could actually be a glitch who knows. When it comes to genetic understanding Mikezumi would be the best available source because it is their element of interest.

My interest lies in the AI elements of the game. The only place genetics and AI cross paths is under the umbrella of 'social events & learning'. Sims with facial features which are either too large, too small or disproportionately put together are at a social disadvantage purposely programmed in and enforced mostly through how the game's trait system works and its effects on what a sim learns. This does not affect actively played sims due to the fact the player controls the interactions, narratives and responses for their sim. Townies are not so lucky.

This isn't to say that a 'less-than-attractive' sim can't live a happy life, they can as long as they aren't saddled with traits which keeps them prisoners to the disadvantage (such as loner, inappropriate and the likes), anything which keeps them away from socializing and social learning.

"large or small" wasn't referring to the size of facial features, rather the significance of the parts of the coding that control functions and gameplay. I have absolutely no idea whether code for controlling the chances of hair colour or facial features coming through, is a small, large, simple or complex part of the code in that area or the whole game. My degree is in Commerce and my current one is in Classics and Ancient History. But obviously code, or what I'm generalising as code because I don't actually know, is an area the modders experiment with and change to achieve the tweaks of the game they do.
But I would think, imagine, that if its not already in the code, the game, it would not be able to be modified. It wouldn't be able to be created brand new. So then if its not possible for grandparents' genetics to come through, if the mechanism for it doesn't already exist in the game, whether in a small or dormant, or large and obvious way (not referring to size of the genetics, but significance of the code), to then be able to tweak and modify, then it wouldn't be in the nraas mod.
They don't get a new face. They kind of change into more of a copy of their parents instead of the interesting blend they seemed to have as a child. Its something addressed by one of the options in one of the nraas mods. When I saw it in there, I thought to myself I've seen that happen.
As far as what you're talking about on a bit of a tangent, the large or small facial features affecting social privileges or attractiveness, its actually multicultural because its a globally distributed game. So in other countries and cultures different looks are considered attractive rather than Barbie and Ken. 'less-than-attractive' is in the eye of the beholder. And actually, in the study of Organisational Behaviour, I learned that less popular personality traits and types, even in the dark triad of narcissism, machiavellianism and psychopathy, those people are still valuable and useful for roles the more popular ones aren't, and that they are even necessary to complete the diversity picture, which is conducive to creativity thus innovation and problem solving.
My screen name Divinyls_Fan hasn't changed since I joined back in the days of Sims 2, in about 2007, so thats nearly 20 years worth (rounding up) of playing on and off, observing and not. Who knows how many sims that adds up to. But I'm not an expert. However I am an expert on my own game, as everyone is.

I wasn't talking about genetics, I had already stated it is not my area of interest. I was merely sharing a few game facts from another perspective concerning how the game uses facial features values in genetics. It doesn't seem my post appeared that way to you.

As far as the 'Attractive Meter' goes, I was under the impression we were talking about genetics inside of the game world, where everything was/is predecided and created. As human beings we have no control over the elements, conditions or realities in our 'real' world if we did no -ism would exist.

While I really don't understand what it was about my post which sparked such emotion in you. All I can say is 'Okay'.