a)I would not like to have children "with" (?) a guy I do not consider my husband. (A bit strange- 'consider' seems an odd choice of verb. However, 'have children with' is correct.
b)I get sad to know that some elderly people live in nursing homes especially because their relatives take them for granted and treat them badly. As I know parents do their best to make their children happy, I take pity on people who end up in life ( ? )like that.
I'd put a comma before 'especially' and I would delete 'in life'. You could change the start to It makes me sad to know...
c) She should change her values of life.
I don't think 'of life' is necessary here.