Tsuna

Tsuna, is the cousin of Sigma Motomiya, and also a tamer. His partner is, which he hadn't received until he made it into the Digital World.

Background
Tsuna, and Sigma, practically lived their entire lives together. However, unlike Sigma, Tsuna hadn't been given a of his own. It was until he enter the alternate world with Sigma, that he met and befriended.

Natural Skill
Unlike most Tamers, other than Sigma, Tsuna actually has the physical prowess of battling rookie leveled Digimon.

Trivia

 * The Sigma to Tsuna combo, is actually another idea I shared at another wikia. Meaning their relationship is deep in heart.