Wait so are they brothers?? (the two black haired boys)

No

i think the uke in the second story was the guy who molested the uke in the first story (not good with names lol) in the train. seeing him made the first couple shocked and the seme even wanted to get salt which what kousuke (i just remembered the name) did in order for the molester (which is, again, the uke from the second couple) to be unable to go near him (kousuke's partner) again