i would let your mom decide what she wants to do. she is probably going through a mid life crisis, you'll just have to step back and let her make her own decisions. if your dad doesn't want to put up with it, that is his decision. i don't think you should spy on your mom by looking at her phone either. i just think she got in over her head.hopefully this will end positively, your mom will realize she wants and needs your family more than this other guy, since especially he has a family of his own too. somethings got to give sooner or later.