Loan sibling money: How to get "paid" back? When you don't need to be paid back.

My sibling's family house got foreclosed. They filed for bankruptcy. Obviously, they can't get a loan. They would like to rent a house. The initial cost (first and last months rent; and security deposit) is about $3000. My sibling would like to borrow $1000. I don't have any debts, except credit card bill. I don't have a family of my own. I have savings. I can afford the loan. Realistically, I don't have to be paid back. Thus, I will provide the money ... cause it's family.

However, I don't want my sibling to know that I don't have to be paid back. I want my sibling to have some sense of responsibility for the "loan". And I don't want to be the easy way out, whenever my sibling needs money.

Any thoughts/suggestions how to get my sibling to feel responsible for the loan?

I'm thinking of writing up a repayment schedule. Or, perhaps having my sibling write it up. Something that we can agree on. But, I'm not sure if there will be any point to it. I won't enforce it--if a repayment is late or missed. Truth be told, it could be open-ended (though, it should have an end date), and it will probably be interest free.

Could this be a motivator for repayment? I'll put in the repayment write-up that repayments will be put aside for future loans. So basically, if no repayment is made, no future loan can be given. If $100 is repaid, $100 is available to borrow in the future. As mentioned, I don't really need to be repaid, I just don't want my sibling to know that.

(By the way, the $1K for the house rental, I plan on paying that directly to the landlord, and not handing it over to my sibling.)