A couple of months back, Benjamin started to say Caleb's name. I think that came first because the two of the are home together so often. Then, just the other day, he finally said Colin's name also. But he doesn't actually say "Caleb" or "Colin."
Which is sort of funny, because we know he can pronounce the "c" in Colin, but he hasn't transferred that sound to the beginning of Caleb's name.