Eustoma_Reyna
I think that Xander's mother is a member of quan clan and Dr yao was sent to protect him from danger
I have a feeling this whole triad business is related to Xander's mother...the way she was trained in combat, the way her identity is being secretly guarded, why she was killed while saving Yera...and Liz mentioned clans going to war due to people falling in love between them...also Sr Yang thought about his wife when Xander asked him if they have any enemies.. I think the pictures with Dion's grandpa will give him a clue..and may be Mrs Yang's name too.