my father's affiar

My dad is 45 around and he is having an affair with his colleague i found out in 2014 and i don't know how much before it started

He always deletes the messages he sends to her always deletes call history I don't know what to do in it can anybody give any suggestions

It doesn't ends here

There's a twist in it too

There's also another women he is having an affair with it but I doubt about that the girl on other side calls him brother but my dad does same here too deletes all messages and call logs and even also saves her name with some random guy name and talks with her for hours

Also here's a twist too

My mom knows all of this things but she doesn't raises a voice against him I don't know why

And when I talked this thing to my grandfather he supports my father's decision and says we have to stay mum

My mother does every things to make our financial condition better and my father goes in job but not earns that much

SOMEBODY'S GOTTA HELP ME