Kurt isn't with Blaine (I don't remember if he even existed in this). Sam and Kurt become really really good friends. They often end up spending the night at each other's houses and wake up cuddling or just really close. I think one of them had an erection once or twice so it's probably rated pg-13, maybe R. There was one scene where the whole Glee club spent the night at Santana's maybe? and Kurt and Sam woke up cuddling, but at this point they were BFFs. Both were completely oblivious to feelings they had for each other I think. They didn't get together until the very very end and there was no sex. I think it was somewhere around 11 parts?
Thanks in advance!