You never know what someone's really like until you live with them.
Even then you don't really know: the Police nicked Sonia Sutcliffe and she had no clue her husband Peter was a serial killer.
Reason I posted:
Beware of the "quiet ones". Sometimes they can surprise you.
A nice guy, very quiet, kept himself to himself, didn't turn up for a nightshift 30+ years ago at Boho - the BA Boadicea House Computer Centre by LHR.
Turned out he was a multiple rapist and he'd been caught.
Story told to me by one of his female colleagues who was my manager at BA and spent many night shifts with him: "We had no idea, he was always so quiet and friendly"...