No, they're not. Benson is Robby's birth name, and he married Karla DeVito (no relation to Danny DeVito) in 1982, and they have two children; a son named Zephyr Segal, and a daughter named Lyric....
i am pretty sure they are not related! They don't look alike at all, they didn't grow up in the same area together, and on wikipedia it says nothing about them been related, if they were related it...