We so often, too often, rationalize ( excuse) manipulative/abusive behavior. We are hesitent to make harsh judgements and more likely to doubt ourselves than listen to what our gut is telling us about the manipulator's abusive character.
As I understand it, he claims to be in outpatient treatment ( paid for by insurance) which gives him the majority of each 24 hour period to do something productive, like work. And yet, he has chosen not to do this and instead, is free -loading off his sister. For all you know, he has abandoned this recovery program or perhaps been terminated from it.
This guy knows your weak points better than anyone. He knows the season. He faces homelessness because he cannot get along with his sister, a pattern. His own survival depends upon his ability to manipulate you into begging him to come home.
Get out of his way and let him fall or open yourself and children up for continued abuse.