We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
You are a middle-aged dad, and there is a nubile young female living in your house and caring for your kids. Naturally, there is plenty of proximity, relaxed familiarity, and time together. Over time, it can feel polygamous. All it can take to ignite things sometimes is just a couple of glasses of wine.
I have seen this plenty of times, and do not believe it automatically means that there is a marital problem (and anyway, marriages almost always have some problem or other). When it comes to light, however, it is a big problem indeed.