A friend of mine who I will call Emma has been with her partner who I will call Mike for 15 years, engaged for 5 and they have three children together. They got engaged after their third child, their first son, was born.
Emma and I went to school together and used to be close but through the years life has taken over and we meet up 1-2x a year max and text each other a few times a year.
Emma met Mike in her late teens and became pregnant by him after several weeks not knowing he had a gf at the time. He and his gf split up and he got with Emma, remaining together and expanding their family to this day.
Recently my sister was at the pub and overheard Mike say to friends that he's with Emma because of the kids, still thinks his ex is hot and saw her at the gym and couldn't stop looking and that he doesn't even know why he's getting married. Later in the evening (my sister thinks he had spotted her by this point) he said he loves Emma really and wouldn't be without her and was just joking earlier.
Is it worth mentioning any of this to Emma? Bare in mind their wedding is next year and I'm be in attendance. My DP thinks it's not worth the drama and pointed out that this isn't a particularly uncommon situation (we have other close friends who have been on the brink of breaking up for over a decade because he says he's only staying for the kids and she says she wants more).
My gut tells me not to say anything but is that cowardly?