I am now having a similar problem with one of my families as well as some other problems.

They are on generation 31 and the new guy has not appeared at all on the details screen as having taken over the house and he has not had one marriage proposal yet.

However, the "next generation" button is still on the family screen and I pressed it to see what would happen. A range of options came up for me to adopt a new peep.... none of whom are the previous generations children! and they have no names! their name place is blank with a flashing cursor.

I adopted a random nameless person... and they are now not on the details screen and have no marriage proposals either....

ETA: I am running .05 and have been since it was available.