My brother is 15 & I found out his is sexually active

He told me he is because I asked & i just try to give him as much info & advice as I can to be safe & the consequences or whatever but he gets mad every single time I try to tell him. I asked him what the plan b was to see if he knew & he said it’s the pill that the girl takes before sex 🤦🏼‍♀️ he doesn’t know everything about sex & all that & I just want him to know so an unwanted pregnancy doesn’t happen. He is just thinking so immaturely. Any advice ?