I noticed today that one of my sims has family members disappearing from their family tree. This problem has never occurred before, my games are all patched and updated (I have Apartment Life and all previous expansion packs), and I have not installed any custom content, hacks, or downloads prior to this glitch occuring.

The adult sim in question has two full siblings which are not showing up in his family tree (they are both alive and on different lots), but his three half-siblings (same mother) are showing up in his family tree. His parents, both the mother and father, are completely absent from his family tree - they died on different lots but their tombstones are still on those residential lots (so far I have not moved another family into that lot yet, so it is unoccupied). Checking the family tree of his half-siblings, who share the same mother with him, only their father appears in their family tree - once he had broke up with their mother he moved out and as I had no further use for him I deleted him from the Sim Bin (a long time ago, before finding out not to do that!). However, when this sim meets up with other sims that are related to him through his mother, such as cousins etc., in his relationship panel they are still classified as "Family".

I'm scratching my head over this one, so a solution would be most welcome!