Harry has alot of gold at Gringotts and its never really been given the attention I thought it would in explaining where all of it came from. They were both still relatively young and I highly doubt they or one of them inherited it from parents.
So I'm guessing that One or both of them were Aurors which leads me to believe that one of the reasons or the main reason that they were killed was that both were highly skilled, and were possibly killing off death eaters, and might have been getting close to finding and or killing voldemort.