Guy's Behavior

Why does my crush's friends tease me about liking him after they found out and can I trust them not to tell my crush?

So today I was in math class and my friend told the two other guys at my table that I have a crush on their friend who was also in that class. I'm not necessarily close with the two guys but we do get along really well in that class and they seem like pretty decent human beings. I made them swear not to tell my crush and they promised that the wouldn't. I thought I could trust them to keep my secret but now I'm thinking about it and I'm getting worried because after telling some of my other friends they said that if they knew if someone had a crush on one of their friends they would really want to tell them. Do you think they'll tell? Also, the rest of the block the guys were teasing me about it by singing the kissing in a tree song with my crush and I's name, joking that we should call him over to help us with this math problem, and they also kept saying his first and last name really loudly. Like they would say something like , "Johnny Smith my boy" and kept calling his name making him look in our direction. Why do you think these guys are teasing me for liking their friend?
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Do you think I should just tell my crush I like him in case they do tell him that way he hears it from me or should I just leave it be?
Why does my crush's friends tease me about liking him after they found out and can I trust them not to tell my crush?
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