does he only like me as a friend?

well i met this guy a month ago and hes is alot older than me and hes my sisters brothers bf and all he talks about is work and what he likes and i dont know if he just likes me as a buddy or what. but he has said that he was interested really or what. but i think im falling for him but its just a friend thing so look for signs of convo's just about him self or that hes smarter than you or is always right bc ur just a bud or hes conceded!