@Xcheldrux Well, the way I see it is that they're both grown men. Add to that, we can almost safely assume that Kurt's wife is out of the picture for whatever reason since he had taken this journey as a nameless, wandering gunslinger. With Evan's dad teaching him everything he knew about how to seduce women while being a proper gentleman; I don't see any reason for Evans to be creeped out or disgusted. Now, if he had started flirting with Oakley, I'm sure he'd have an entirely different reaction.
@friedtofu Yeah I'd already assumed Evan's mother had passed away at some point. My main issue here is that this gives the impression that his dad didn't care much for her, his attitude of "as soon as you're independent I'm leaving so I can be with more women lol" doesn't do much for him.