My baby's stuck alone

See it says the rue family here but it's only him 

 Help guys I have a sim who as an infant son and then she married a pregnant sim who couldn't move in with her so I moved in my sim that has a son with the pregnant lady but when I checked I saw that my sim didn't move out and into the other house with her son and now the son is left in the previous house as the owner and when I try to relocate the baby he dosen't show up in the family slot or single sim slot and the sim and the pregnant sim are in the family slot without him help idk what to do