IF the money had been a loan at the time it was made, he might still have time to take legal action to recover it: the statute of limitations (or time to sue) in MN is 6 years for both contracts and  promissory notes, so depending on the extact time frame, he might be able to take action.That is assuming it was a loan, however. If the  money was a gift at the time it was provided--that is, it was made without expectation of repayment--he cannot after  the fact convert it to a loan; once money is gifted, the giver has no right to its return. Of course, if he "remembers" things differently, he can (assuming he is still withing the statute of limitations) try to sue you and prove it was a loan; he would need to be able to prove by a preponderance of the evidence (more likely than not) that it was a loan, not a gift, and you could provide your own evidence or testimony to show it was not a loan. Without some actual promissory note or written contract or agreement to repay, the advantage  would lie with you, since as the one suing, he'd have  to affirmatively prove his case.The letter you describe, by the way, does not seem to prove that it was a loan--the language your quote says nothing about the money being loaned--and would likely not have been enforceable had you passed away, since it does not appear to meet the requirements to be a valid will.