I agree, my main sim has 4 children with different dads a set of twins from one and one boy from another and a girl from another but when I open the genealogy tab for the twins their brother and sister dads arent even on there and vice versa. I get that the twins aren't related to the boys dad or the girls dad but it should still show their dads on their tab, from their point of view it's like their siblings don't have dads and I find that weird cause they're all part of the same family. I have a many generations legacy family and the amount of times their 'ancestors' call inviting a long removed family member on a date is just silly or they'll met them out and about and start flirting, it's kind of creepy. My sims might not recognise them as family members but I know who they are 😂