Keep this matter as family problem. No need for IOUs.
Your elder sister and her hubby are in deep shit.
They use money they did not have. They are supposed to
generate money with the money they borrow. It is not unusual.
In business some make money, some lose money. No need to guess
which category they are in. Now they are in a mess, as they must
return what they borrow.
They can't re-pay you, at the present moment. You must
understand that. They have to take care of non-family members
first. That is their creditors, vendors, contractors. etc.
As family member, talk to her, don't ask for the money back, but
tell her now its your turn to need money. And that money you
lent her could come in handy.
Keep the relationship, if have to sacrifice the money.
Also let this be a lesson, NEVER lend money you cannot afford to
lose. People have lent life savings for retirement, much to their
regret.
