Loneliness.
The Bible says 'He sets the lonely in families' (though not having a computer-based concordance i can't just tell you exactly WHERE....).
When we think about the word 'lonely' we think about feelings but I wonder whether the Lord is not just dealing with those who are self-consciously deprived of sufficient human contact but whether it is that He sets the ALONE in families. There are plenty of people living on their own, with their cat, who wouldn't call themselves lonely. However, the fact that their contact with fellow humans is so very limited is not beneficial to them as developing people; though, I daresay, given the opportunity for a bit of solitude most of us would be glad of it.
Being free of the demands of other people - liberated from the duty to THINK about someone beside 'myself', one could read lots of books, play whatever music one liked, never have anyone criticise or contradict and NEVER have to try and deal with someone whose mood and attitude baffle and frustrate one - hey ho, the Lord knows what's best!!!