My boyfriend's family is a single-parent family, my mother is deaf, and she has two sisters and one sister. My parents don't know about his mother. What should I do?

Your boyfriend is very capable, promising and responsible. You don't have to worry about his family. Sisters will get married in the future. If you marry him in the future, you must and have the obligation to take care of his mother. As for the fucking situation, if you have any plans to get married, I think it's better to find a better time. When your parents are in a good mood, after a while, your parents think your boyfriend is not bad, so tell your parents the truth. After all, deaf people should not inherit any serious illness.