You know, over the last few years reading this particular story thread, I've gone back and forth in my opinion on how Randy has dealt with this endless Sean Situation.
I know they're supposed to be kids, but it's getting to a point where it's hard to keep giving someone the benefit of the doubt. Sean is a snake in the grass, and the worst part about it is, Ryan knows this information. I know Randy has some self-esteem issues, he doesn't see himself the way everyone else around him sees him, and that could be informing his sorta-kinda paranoia, but honestly it's not Previous to the spring break events, Ryan just had a massive blind spot about what he was doing with Sean. Or what kind of person Sean was. But after Randy heard Sean admit to exactly what Randy had been paranoid about, and Ryan knows this information. The fact that Randy sees this "connection" between Ryan and Sean, it's there, and it's poison for Randy and Ryan's relationship. There's a kind of cheating that can occur before actual cheating takes place, and that sounds an awful lot like what's happening here.
The bottom line is, Sean isn't interested in being "their" friend, he's interesting in coming between Ryan and Randy. No matter how much Ryan reassures Randy, the fact that he's allowing this whatever with Sean to perpetuate, while knowing what he knows now, he's honestly not a good boyfriend. I know he's Randy's first love, but whether Ryan likes it or not, it's going to come down to a choice Randy or Sean. The fact that he hasn't already chosen Randy and sent Sean packing does not the future with Randy.