Hitting Bottom

My brother in law brags about his sports betting but the strange things is that he and my sister have to live in a tiny apartment because they never have any money. What is up with that then? He claims to have a football betting system that can’t lose. He bets on every game every week and for each game he places multiple small bets like first half score and other things and then he doubles up on any bets he loses until he wins it and then he stops. It is a pretty smart system if you are willing to do the work but where he goes wrong is he never stops betting when he wins so the money never comes in. He won’t admit that he has a problem and he argues that it is like a scientific program. He has an answer for everything. My sister is getting really fed up with him. How can I make him admit or at least see that he has a gambling problem?