Quote CherylD: The little girl who plays Summer is 7 in real life. I can't imagine they cast a boy who looks that much older than 7. And Fen would be more advanced than Summer - he didn't eat peanuts that he was allergic to that made him revert in age and have to re-learn things. My guess is that they cast someone like that to show the contrast between Summer and Fen -- remember, her mental growth has been stunted some because of Mary Jane.
That would be the logical way of storytelling, but these writers never let the new Fen talk. He is only allowed to yell out one or two word phrases. It is beyond dumb considering he has two of the smartest people on the show as parents. But they again, he never has scenes just at home with his parents. The actor is actually younger than the girl who plays Summer, but he is taller.
Fen is no big deal for these writers. I have no doubt they will show Fen once more for Christmas before shelving Fen for the next 10 months just like they have the past two years. They have little interest in writing for Lauren and Michael or their son Fen. He has only been on three times all year including this Thanksgiving show. Little Delia has been on many more times in her first 9 months than Fen has been on his own life.