There are several connections between the two, actually. Hwoa... Haow.... Bob and Yunsung are likely related. They're both Korean, they have that same fiery hair, similar fighting style (lots of kicks), same attitude, etc. Yoshimitsu in SC is the founder of Yoshimitsu in Tekken's clan. Some people thing that Xiaoyu might be a descendant of Xianghua, but it seems like a bit of a stretch.

Soul Calibur > Joel