Sanji was a helper out by your house. You were rich and young, but also someone who cared for your younger brothers. It's not like your parents died or anything, but they didn't have enough to take care of them, so you took them off their hands. With work getting busier, you needed some extra help.

When you thanked him, he just smirked and shook his head, rubbing your shoudlers. "It's nothing, princess."