if you've read my other topic about shenhua's flashbacks then you'll no i've been thinking about the shenmue tree and its connection with shenhua, well this kinda leads on from there cos i think Yu susuki gave us a big clus to shenhua's/ryo's in the shenmue tree scenes.
when there looking at the tree together ryo mentions the cherry blossom back home, i think this represents his fahter Iwao. But he also feels the same connection with the shenmue tree, as does shenhua, so i think shenmue represents their mother.
ryo and shenhua would make sense, afterall both mothers are dead, neither of them remembers their mother and they have the same nostalgic feeling about the shenmue tree.
Problem is we don't no when Iwao visted gulin.
see i think when iwao went to gulin he started a relationship with shenhua's mother (obviously shenhua wasn't alive then as shes 2 yrs younger than ryo) and they concieved ryo. but then iwao was drove away for some reason and took the mirrors and ryo to safety.
2 years later shenhua's mother is still in gulin and in a relationship with shenhua's father and she is concieved.
i dont think they share Iwao as a father as that would mean iwao made 2 trips to gulin or lived there for 2 years!
hopefully we'll find out in shenmue 3!