Why are they so ugly?

The problem in Sims 2 is that they actually look too much like their parents. 

Later games do a better job of combining elements from the parents and applying them in a way that works fairly seamlessly. In contrast Sims 2 is very basic in how it does it. It literally takes bits from each parent and puts them together on a toddler's frame. Which, of course, looks weird. They have to grow into the bits and tend to look normal by their teens. Even then, some combinations of bits may still look odd. One parents eyes with the other parent's nose may not quite work on their face shape. I have a mod to allow me to use the plastic surgery object starting with teens so I can fix any bits I don't like as soon as possible. The only way to guarantee you will start out with a good looking toddler is to make one in CAS. If you encounter a premade or townie toddler Sim who is attractive, it's because they were created in CAS.

Yeah, I've noticed that. The toddlers and kids are such hell spawn but then when they are teens, they are smokin' hot. Literately, when sims walk by, they do the whistle. Once, one of my sim's older brothers girlfriend did that every time she walked by him. But not with her actual boyfriend.

The weird part is, when I'm creating a family, I could just get 2 random sims out of the sim bin then play with genetics. The toddlers and kids and teens that come out of them are actually decent. Like pretty playable. But then, I'll take ages making a perfect couple, symmetric features, nice hair, not too different-not too twin like. Then I'll play with genetics. And oh, my great god. I already explained how ugly they are before, so I won't again. It just frustrates me.

The wolf whistle indicates there is something in their turn ons that makes them compatible. I assume they have at least one lightening bolt on their picture too. If I have a couple I want to keep together, if they do not have at least two lightening bolts, I have them drink re-nuyu porta chug and change their turn ons to be more compatible.