in the first season Bone's is telling Booth about her experience in the foster system and how she was in there until her grandpa came and got her out of the system.

In season 3 she is in the diner talking to her father and he gives her a piece of jewellery that used to belong to her grandmother, upon hearing this Tempee turns to her father and says that he used to tell her and Russ that they never had any grandparents. Max admits to her that her mother and him agreed it was better if they never knew they had any grandparents.

If she never knew her grandparents and she'd changed her name how did her grandfather find her to get her out of the system? and why was she so surprised all those years later that she had grandparents that were alive?