It sounds like a good idea on paper, but like too many issues this government are trying to tackle in order to try and present themselves as tough on benefit cheats, it's too complicated. Situations with joint custody, older children coming home from University for the holidays, rooms being renovated... all bear complications.
Personally my mum's just moved into a three-bedroom council house - strictly for her, my younger brother, and my niece (who she has guardianship over... there was a long and bitter custodial battle between her mother and my older brother, but they both still see her and get along now). My sister's just turned 18 and is expected to find her own housing, and I am too. So at the moment I'm sharing a bedroom with my brother (which isn't ideal but he sleeps downstairs a lot when friends are over anyway
), my sister has her own room (unfair ¬_¬ LOL) and my mum uses my niece's room when she's at her mother/father's (which is more often during the holidays than it is in schooltime).
I'm not entirely sure where I'm going with this
but presenting myself and my sister (who is employed, but not making enough to afford rent on her own even for a flat, since South Devon housing prices are probably some of the highest of the country). Torbay's a total mess, really - the highest teen pregnancy rates of the country, and some of the longest waiting lists, so I shouldn't complain really.