I often wonder this myself also. I think it is a fascinating topic to muse on. When I see pictures of myself as a youngun, I look just like my maternal grandmother, but everyone has always thought I look like my father. I concluded my parents must have been related.

Both my kids have bags under their eyes and I have a picture of a great-grandmother and her sister when they were little, and they both have the bags going on. And from my mom's side, there is a whole issue with blood flow and clotting that is at least 3 generations through.
My son is color blind, like my dad was, and sometimes it bothers him and sometimes he likes being like Grandpa. I like that he got that from my dad.
Even though we can never learn to what extent, I like to think our ancestors spirit lives on in us somehow.
Kath