All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If what you said about your mother is true that she has illicit relationships with men, then she is undoubtedly wrong and sinful.
If you mean that you hate her doing those things, then you are not sinful about this; and this is even something religiously required and it is a sign of good faith. However, you are obliged to be kind and dutiful to her, and it is not permissible for you to mistreat her at all. The best act of kindness and dutifulness to her is that you should advise her in a soft and gentle manner and be keen to turn her into a righteous woman. For more benefit, please refer to Fatwa 86378.
As regards those men, it is not permissible to let them enter your house or be in seclusion with your mother, sister or any other woman. Therefore, you are obliged to prevent them if you are able to do so, or seek the help of your relatives or any other person who may prevent them. You may also threaten them to take the matter to the authorities.
Allaah Knows best.