I need some advice

Hi i just found out my little brother who is 18 years old watches gay porn on the computer and i have caught him watching it several times. So when i ask him real serious he keeps denying it. So i want to be a good brother (im 100% straight btw) and help him. But im scared he might not be gay and i will push him to be gay. I need some advice should i confront him again and tell him i know he watches gay porn or should i wait for him to tell himself. Thank you guys in advance