Just the other day I sent my guy to Egypt for a second time. A friend of his there had died of old age prior to that, but when he appeared at the base he had a negative moodlet of witnessing death, his LAST NAME was changed to the one person's last name AND he'd gained an adult daughter with a woman I'm not sure he even really knew that well... And even the 'daughter's' half-sibling was in his relationship panel.
I had basically the exact same problem the other day. I sent my girl to Egypt with her daughter because her dad was from Egypt but when I got there she was heartbroken from witnessing death of some old random guy. I was looking through relationships to see if he was still there via bugs when I saw a teenage boy with the family icon. 'Son'. The old guy I saw in family tree had taken my last name and now I had this almost full grown son, in Egypt no less.