Looking for a very old story that had once been elsewhere

Looking for an old story that I am at my wits end.
It was a serial. there was a housefire. boys skin burned to a crisp and sister braindead, spo they place her skin over his body and convince him he died & his sister whom he is convinced through hypnosis etc believe to be his own sister. Read it originally on crystals storysite.
Assistance appreciated