It's harder to see in the photos than in person. In looking through some of my old pictures of Thomas I think they really could pass as pictures of Gabriel; I just don't have all the photos to match up.
Gabe does have his own expressions and differences, of course; for one his eyebrows are typically either crunched and serious or drawn high in interest or happiness. I'm sure he will soon take on some of Tom's mannerisms though, particularly with how much Thomas just loves entertaining his little brother. If only I could, I would show you how sweet it was this morning when Thomas came in to bed with us, and every time he laughed Gabriel smiled from ear to ear.