You never claimed to be dead. So it seems that's not illegal. If your family really thought you were dead, they didn't do anything illegal either. Could they be forced to give the money back?
I imagine the legalities of being declared "not dead after all" would be pretty difficult.
But having even a $1 life insurance policy, or $1 in debt, or accessing $1 worth of a reputation-based benefit, might be enough to demonstrate that intent. Most people in the US could not fake their own death without criminal or civil consequences.
We no longer have the "move to the New World" or "move out to the frontier" reset buttons that previous generations had (nor even the "get sentenced to transportation" and "claim sanctuary" buttons).
https://en.wikipedia.org/wiki/John_Darwin_disappearance_case
He wasn't charged with anything because he never pretended to be dead (and also because he was legally dead and therefore tricky to prosecute). But, he went before a judge and totally failed to get the declaration reversed. Last I heard, he's still just dead for legal purposes.
http://www.dispatch.com/content/stories/local/2013/10/10/jud...
This exact situation happened in Ohio a few years ago. http://www.nytimes.com/2013/10/12/us/declared-legally-dead-a...