Might it have something to do with Mortimer being in a similar age group to his parents? You might try aging Mortimer down and then see if it works.
I too make extended families and break them off, usually from making a nuclear family snd then adding grandparents, bothers and sisters etc. ( without using full edit mode ). And I have noticed in some instances if the parent and child are in the same age group it won’t work.
Also with Agnes (from country living)…. Isn’t the one in game made to be immortal and non playable? I thought I read something about that.
I hope someone can help you make it work,
