The person you have fallen in love with is already in a relationship, moreover, that partner is your friend. What will happen in such a case... Of course, you think you will secretly continue to suppress these feelings, but it is not going well, and you are doing your best just to suppress your feelings. You also surprised yourself by thinking that it might be better to convey your feelings to the other person.

If you were to confess your feelings, not only would you lose the friendship, but your credibility would also be lost. Since no one benefits from this happening, how about just watching over the other person?

Please do not take any actions that would interfere with the feelings of the two. Not only does the possibility of losing friendship increase significantly, but also that lover will never have a favorable impression of you. However, if you watch over them properly by their side, the opportunity might come around to you, the closest one.