Can a man be forced to move out of the family home following divorce when paying half of the mortgage?

My son is divorced and living in the family home. He is paying half the mortgage and has been for 3 years. He is ill with mental health problems, she has told him that she wants him out so she can move in as she is paying the other half of the mortgage. Can she force him out? She left him over 3 years ago and did not want the house until July this year. She says that if he doesn't move out that her solicitor has told her she has other options. Can she force him out?