<human>: Can you give me the gist of the text in a nutshell?

As a single person, I obviously hang out with many friends that are coupled. Over the past few months I have been spending a lot of time with one couple - Admittedly in part because I was attracted to my friend Rob. Also because we all have fun together.

Rob and Katie's relationship seems relatively dysfunctional. Lots of nagging, and berating that reminds me why I am happy to be out of MY old relationship of 5 years. Additionally, Katie has some serious issues with substance abuse. Whereas Rob and I certainly like to drink, party, and have fun.. Katie takes it to concerning extremes.

Over the past few months Rob and I have become closer solely out of the time we've spent together, but also because we started texting a lot. I didn't want to admit it was flirtatious at first.. Even though I knew it was. We ended up exchanging naked pictures, and having pretty frank, sexual conversations. This was obviously crossing lines, and I knew it - But I like Rob. And admittedly I haven't felt such sexual tension with anyone in my life. We ended up secretly hooking up one night while Katie was gone.. Since then our texting has definitely dwindled, and hanging out obviously feels really weird. Katie confides in me that she gets so frustrated with Rob, and tells me some of the extremely asshole things he does to her, but in all "he's really good lately.." It's uncomfortable for me to watch when she drunkenly snuggles up to him, and kisses him. And it's hard for me to hear what a "good" guy he's been lately making her dinner, or having movie marathons - And I actually find myself weirdly jealous because again, I like Rob, and I guess I miss the perks of a relationship

How can I stop feeling this jealousy?
Why doesn't he just break up with Katie?
<bot>: Slept with my friend who is in a seemingly dysfunctional relationship. Since then, I find myself really jealous and confused that they're even together in the first place.