My reaction to your question is - don't do it! If you go ahead, you too will end up in financial disaster and be just as much a victim as your sibling is of the criminal relative who conned your sibling into spending money and time looking after them while selling the promised house over their head.
The local authority has an obligation to house your sibling, and they will get some money to tide them over for the short time that they believe it will take until they are earning again. Meanwhile, if you go ahead with your idea, you will have lost your home - and half your future pension. You are NOT deserting them by sending them to their council offices for assistance, and keeping your own money fto offer practical help in smaller things.
Forgive me if I am wrong, but this does read very much like a what-if plot for a novel or a magazine article, as I have thought that other threads of yours have done in the past. Why ask strangers on a social media site, when advice from the Citizens' Advice Bureau, AgeUK or a legal expert would be much more useful to you and to your sibling?