So, basically, my dad is single. My dad's friend is married. And I can say with about 95% certainty that I saw them make out next to her car.

I had a feeling this would happen, or already was happening. He'd been telling me how he felt about her, and I had seen some things that were pretty big tells. I can't say I disagree, he is a better match for her than the person she's married to, but fuck man I didn't think this shit would actually come to fruition.

I'm not gonna lie, I don't necessarily care that they're cheating. I'm a neutral party for the most part, but she has two kids. One is an unstable middle-schooler, and the other isn't even 10 yet. Additionally, the guy she's with isn't a bad guy. One thing's for sure, if they get had, the fallout will affect them a lot more than it will me.

I'm not sure what to do, here. I feel like suddenly I have to try to resolve this situation before things get out of hand. I know my dad probably won't listen, I've already told him not to do it, so now it seems like I've got two options. One, I convince her to stop things, which will be difficult because I would hardly ever get a chance to catch her alone, or two, I ignore the situation until shit happens, then do as much damage control as possible. I'm not going to tell anyone unless asked AND PRESSED about it, because at this point, spilling it is going to do more harm than good.

Anyone have any advice?

The one who is the root to all this is the woman, isn't she? I am not entirely sure how to confront her, and I do acknowledge that it may be difficult to do so. But I do believe she needs to make a decision rather soon, one way or another. Convincing her to "stop things" isn't necessarily the best thing, but at least press that button to try to make her feel guilty about what she's doing. As in, trying to talk to her in order to make her make a decision who she wants to be with. Because... she quite plainly cannot have both unless her husband agrees, and I quite doubt that to be the case. Then again, you may be misunderstanding something, in which case she should be given the chance to defend herself. ... Not saying that defense might not be filled with lies, but in either case.

I'd say call her, tell the house that you want to speak directly to her, and then try to make that happen somehow. Then ask her, speak to her and press her about it. Of course, then there's the question of if she'll react like a sane human being or like a child. That's what I think. And perhaps give your father a piece of warning, but yeah, it is her fault to begin with so beyond a warning shouldn't be necessary.

I'd also like to mention I have zero relationship experience and the above is all from watching love-dramas, but in any case. I felt like I should make my input. That's all.

You could just, y'know, let consenting adults make their own mistakes. Raise your objections, then let nature take its course. He may be your father, but it's not your problem.

Right, so I had a talk with my dad about it, and he explained that they were just hugging for, like, 5+ seconds. He has also said that, even though they both know that my dad is, like, madly in love with her, they haven't done anything line-crossing. Not sure I trust him entirely, but I'll give him the benefit of the doubt on that.

He also explained that there are other things going on that I wouldn't have counted on. It's still a bit of a harry situation, but, if my dad is to be trusted in this regard, no actual cheating has occurred.

I've heard stories about the family that used to own the hardware store that I work at and my dad now owns. Once upon a time one of the old owner's sons was out doing kid shit in the 60's and driving around like in American Graffiti. Eventually they come across a parking lot where his friend points out to him: "Hey, is that your dad's car?"

They drive up to this car to find the old owner of the store making out with some other chick. He sees them, and they see him. So they leave. But the old owner's son is sitting in the passenger seat smiling like a victorious champ. His friend asks him, "And what are you smiling about?"

"I just got a brand new Cadillac." he says proudly. And promptly gets on the next morning.

And that's my addition.

Great story. Sadly, I'm not conniving enough to blackmail anyone.

Right, so I had a talk with my dad about it, and he explained that they were just hugging for, like, 5+ seconds. He has also said that, even though they both know that my dad is, like, madly in love with her, they haven't done anything line-crossing. Not sure I trust him entirely, but I'll give him the benefit of the doubt on that.

He also explained that there are other things going on that I wouldn't have counted on. It's still a bit of a harry situation, but, if my dad is to be trusted in this regard, no actual cheating has occurred.

Then that's honestly all you can do right now.
As much as the cheating can hurt her children, this is something you have limited knowledge on.

On top of which, it's an issue where nothing wrong has been proven.
And even if it get's proven, the way it's exposed could be more devastating to the children than anything.

In other words, the best you can do now is sit back and trust your father again.
Reconsider perhaps once you see something that may confirm it, but for now acting any further wouldn't be wise.

Some pretty valid points have been raised, my mother was subject to a similar situation as well as my aunty. The whole process ended up ripping both families apart, but there were other important details to factor into those causes. As someone with some experience from a similar situation, staying out of it and standing on damage control is your best bet, take your dad's word for truth and pay the situation no mind. If their conduct makes you uncomfortable, maybe bring that up with your dad, it's possible their doing something that they don't realize can be perceived as inappropriate or suspicious from an outside perspective, which could create problems for them if another party is viewing these actions.

When I tried to intervene in my mothers antics, I only got emotionally hurt by her. Her situation was a lot easier to deal with when I took the step back, looked after my younger brothers and dealt with the after-math the best I could. When I tried to get involved with my aunties situation, I ended up spending some time in jail for assault. Honestly, I can understand how you must feel, caring for dad and hoping for the best for him, but it's easier for you both if you just let it play out and deal with any collateral should it arise.

My uncle let's call him Thomas.
My aunt let's call her Tabitha.
A family friend & neighbor let's call him Timothy.
Timothy's wife and employee of Thomas let's call her Tess.

Thomas is related to me and my family by blood. Tabitha is related to me and my family by marriage.

Tabitha was banging Tess (I walked in on them).

Tabitha & Tess both ended up broke, homeless, and without jobs since they violated their prenups.

Tabitha has supervised visitation rights of her kids that Thomas has sole custody of. These kids are now in therapy because of Tabitha's action during the divorce.

Cheaters are horrible people they should be shunned.