Hi there I would like to begin by pointing out that if Adam really "loved" you as much as he says he does, he would respect the fact that you don't want him in that way and back off. If he is pushing anything on you, it is not only disrespectful but shows that he is willing to put his needs above yours. This is a red flag of things to come. Any indication that he cares more about his needs and what he wants out of things then what you want or need is a very bad sign of things to come. It's really good that you put your foot down when he started kissing you, however instead of "softly" pushing him away next time (assuming there is a next time) give him a nice hard shoving. He needs to remember that you are happy with your boyfriend and he has a girlfriend.
In case you were even considering being with him, please note how "faithful" he is to his current girlfriend. If a guy with a girlfriend is hitting on you; it is a really bad omen and basically proof that he could do the same thing to you. If he has done it once, he will most likely do it again. I believe the current statistic of repeat offenders (in a general sense, not just cheating.) is 77 %. I don't know about you but I am really uncomfortable with those numbers.
As for Luis, I would expect him to easily get jealous of Adam. Especially if you are very friendly with him. I realize that just because you are friendly doesn't mean that you like him, but it's really hard for Luis to understand that. He hasn't been around the entire period of you and Adam's friendship and just because it is the daily norm for you and Adam to act a certain way towards each other doesn't meant that Luis is going to understand.
Honestly, if Adam continues making inappropriate passes to you I highly reccomend that you stop talking to him so much. It would be respectful to Luis. How would you feel if Luis's best girl friend was constantly all over him and making passes at him? I know it would make me very uncomfortable with the situation and I would feel a lot better if they didn't talk as much.
I know that seeing Adam less is hard because you probably do love him. If you both have been close your entire life then you probably "love" him but that doesn't mean that you are "in love" with him. If you aren't in love with him then it's really not fair to lead him on because he obviously is in love with you. Maybe it would help you move on from his friendship if you looked at it as you hurting him.
I haven't mentioned this yet, but do you think that you may be in love with Adam? If you are even questioning it; it would probably be a very good idea to break up with Luis. It's not fair to him if there is a possibility that you have feelings for someone else. At least be single until you figure out exactly what it is that you want. Relationship limbo is the best for these situations.
What can you say to them?
Well that's really up to you. I just advise being honest with them. In order to be honest with them, though; you have to be honest with yourself first.
Do you love Luis?
Are you in love with Adam?
Would you be willing to let Adam go for Luis?
Would you be willing to let Luis go for Adam? etc. etc.
Good luck to you.
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Antidisestablishmentarianism.