I need advice.

I have a crush on my best friends brother. I know. It seems like something out of a movie. It’s not like a “omg he’s so hot” it’s like a “he’s cute, and has the same interests as me, and his personality is amazing” kinda deal. (He’s 4ish years older) any advice? I don’t wanna tell my bestie, obviously bc I don’t wanna ruin our friendship. But I Snapchat him and talk to him a lot, I tend to be more energetic when he’s around, I think she’s starting to suspect something. I’m terrible at keeping

low key if someone I think is cute is around, ugh. I just don’t know what to doooooo

Edit; I’m 14, he’s 18. My bday is in January. I’m not looking for a relationship(obvi, it’s illegal) but just some tips to keep low key? Idk what to do