Worried about boyfriends brother

My boyfriends little brother lives with him. He's 15 and has a YouTube gaming channel. He's not well know but had gathered a decent following for his age. He puts his Facebook in the description of his channel in hopes.to !make.friends with people who watch his videos. He's autistic and has trouble making friends. Well I found out he's had a lot of creeps message him. I've seen both older men and women message him asking for sex it's. One was from a prostitute saying he would pay HIM to sex. The text messages get even more disturbing. He said he was feeling worried because someone texted the street he lived and and said they would hurt him. That was really scary, but besides that situation it doesn't seem like he understands how dangerous this is. He posted a picture on his Facebook with his new puppy and someone commented yummy😈. This all just seems so dangerous. My boyfriend doesn't know about most of it.