Mary, I feel for you! A number of years ago, following a serious stroke, DH decided to "help friends get back on their feet" to the tune of nearly five figures! No agreement about repayment was formalised, though they did make a few payments to him while he was around. I asked what would happen if he died and he told me they wouldn't let me down. Well, they have let me down and I am in a financial mess at least temporarily as they consider their debt was to him alone! Over the past year I have had to face possible homelessness and bankruptcy, but our lovely offspring have come to my rescue!
I'm with DotMH on this. I would advise being very, very cautious in a situation like yours. You need proper advice about your sibling's position - what benefits/help with housing is available; whether they are entitled to carry on living there at least until your relative dies, or if the property needs to be sold to pay legal fees; could your convicted relative appeal on health grounds that a prison sentence is inappropriate; whether any agreement was properly set up and witnessed etc etc. Selling your property to rehome your sibling in this sort of situation has far too many pitfalls for the ordinary person to negotiate and you yourself could end up penniless and homeless.
Best wishes, and please be careful