For a while we've been suspicious about some of my dad's behaviour (being horrid to/about Mum, going off on mysterious trips, zealously guarding his phone, deciding to buy a flat which mum doesn't know about). Today my little sister (who still lives at home) came round to see me in tears because she'd been snooping on his mobile phone and found messages which were obviously from another woman. Now we don't know what to do. Should we confront him? My brother said it might make him leave mum. Sis wrote down the woman's phone number, so we could ring her and confront her, but I would feel less comfortable about that. He should be held responsible for doing the dirty.
We just want him to stop seeing this other woman. We don't want mum to find out. She may have suspicions, but to have them confirmed would be devastating. They've been married for 34 years. She has devoted her life to her husband and family.
I'm eldest of 4, so my lil sis and brothers think it should be my responsibilty to talk to him. What do I say and how do I do it?