Mother telling the son to never remarry

If a man got married and his mum told him that he must not marry again and he's been through hell in his marriage. His mum is late now amd his kids are grown up and working. He found somebody in his life who is going through as much as him. She was an orphan and now he wants to know if he can marry this woman despite what his late mum said. He is only living in the house because of his kids. Can you advise if he can marry and be happy again?