He has a little brother named Chisao, who thinks Dex is the best Netbattler in the world, and Dex himself tries to maintain this respect.
Dex is very arrogant and boastful. Even so, he cares deeply for his brother, even panicking when he gets in trouble. He shares a competative but still friendly rivalry with Lan. The two often compete whenever they can, usually with Netbattles.
Despite his strong and boisterous demeanor, he does care very much for his friends and is willing to risk himself for them. He is also shown to get somewhat emotional, an example being when he moved away to Netopia.
Dex also seems to have a great interest in curry. Even taking up a career in preparing it later in the anime.
Dex has only gained weight once in the anime.
In Episode 54: "Chisao's in Town", he along with his brother and Lan became very stuffed after eating a vast amount of free curry.