I haven't got the description for T.K from the official site, I did write it down but I used yellow and it won't show on my paper so sorry to all T.K fans.
Description in book, by Tai:
I can describe T.K. in one word: small. But he's only eight years old, so I guess that's natural. And to be fair, he's a lot braver that I was at that age. I mean, he does spend a lot of time trying to impress he's big brother, Matt, who he really looks up to. But everyone likes T.K. because he's such a nice kid. Not to mention, when we're being attacked by scary Digimons like Seadramon, he stays pretty calm and relaxed. How can you not like a kid like that?
T.K is the youngest of the group and that would explain some of the crying in the first season but don't be hard on him, you try to go to Digiworld when you're six or seven.