For perspective, the entire downstairs footprint - including the hallway and toilet - is smaller than the open plan kitchen/living/diner in the one bed flat I used to live in.
Served wonderfully for one person, with room for the sofa bed for guests etc - for a family home, not a chance!! You'd be on top of each other all the time and it would be so loud when you were cooking, had washing machine on etc.
Also storage as others have mentioned - where are you keeping shoes and coats? Suitcases? Spare linen? Where are you sticking a clothes horse with clothes you can't tumble dry in winter?
I can't see room for anything like that - and no room to build any more storage in!
A big no from me!