Parental Changes on Sim Death After Adoption

I don't have any screenshots of the tree before the bug, but you can see in the adopted child's (Levi's) and adopted parent's (Tasha's) genealogy that my dead sim's parents and sibling became the parents and sibling of Tasha. All I did for this to happen was have Tasha legally adopt Levi after his bio mom died. Bio mom is erased from the family tree, but I don't think that part is a bug because I'm not sure how the Sims would keep both parents in the tree anyway. But bio mom's parents/brother shouldn't have become Tasha's just because she adopted their grandson/nephew