Is this boy i love Gay?? PLEASE HELP!?

first of all i am a GUY...well i have a bestfriend who is a girl and her brother is so cute and the first day i saw him is when came to spanish cl and sat right diagonaly behind me and he always stared at me everyday! and this girl that sat next to him always made gay jokes like "oh he likes big boys like you" and "he's your baby daddy" and he never got mad!...so then one day he moved to another seat that was an easier way to stare at me from! and he used to start smiling whenever he saw me in the hallway or either smiled....one time in spanish cl i told him i liked his legs and he just smiled and laughed....and one time i went to his house and i caught him staring at me many times...i asked him why does he stare at me sometimes and he said "stare at who" and i said ME and he didnt say anything he just kept walkin! to make it shorter basically he stares at me when im not lookin! when he comes 2 skool with his sis he always used to smile when ever they came up 2 me