It's been my 'fear' that my financially incontinent DB (52) will screw up sufficiently to need to move back in with our mum. She doesn't want it but says 'I'd never see you homeless'. It wouldn't worry DB one bit, the ignomy of having financially so failed to be 'an adult' that he needs to fall back on 'going home to mother' (he was 36 when he left!). Mum's will leaves 2/5 of everything to him, 2/5 to me and 1/5 to 'any GCs' (whom I have, both of 'em!). I hope that, should he move back in, mum won't be coerced into changing her Will, but she still, despite overwhelming evidence to the contrary, sees DB as being 'unlucky' rather than 'feckless'!
DH (51 now) and his DB (59) were each given 50% of their last parent's estate, 10 years ago. DB never left home (he was unnaturally close to his parents, his mum in particular...) and has become very well off, having never paid rent or supported any one else. To my continuing (but silent!) irritation, DH decided that his DB's half should be the huge house ('We can't throw DB out!'), with pool and all the furniture, and the family car (in Oz); his own (DH's 'share') would be his father's pension fund. DB's 'half' is currently worth about £500,000. DH's 'half' pays him £400 p.a.
The house is far too big for DB on his own (and he moans about that all the time, having to mow half an acre, pay for a cleaner etc) so he's now talking about selling it. Says it's ridiculously big and he rattles around it all by himself....
I personally really believe DH should have demanded half the house, with a 2 year get-out to his DB. Not only would it have ensured some parity- we are the only ones with DC and uni fees ahead, DB is completely single! Like my DB, actually, only much better off - it would have forced DB to 'get on with his life'.
So I am entirely with you!