Strange cousin

My boyfriend (of 2 years) has this step-cousin his same age or maybe one year older I'm not so sure, but anyway when we all hang out with him I notice strange things he does to my boyfriend. Whenever my boyfriend is driving and his cousin is in the back seat he start massaging his head and neck. Whenever we are all laying down on the big sofa downstairs watching a movie, he stroaks his leg. He is always (when I mean always I really mean ALWAYS) talking about penis and balls. When we go to the mall he's always checking out guys, he's always telling me OMG I love how sexy that guy looks..... BUT IM NOT GAY IM NOT GAY NO HOMO!!! he's only dated girls in his life. I personally think he doesn't want to come out of the closet because he has a very strict father that would look down on him if he would come out as gay. I honestly think it's ok to be who you are but he's making it very difficult. He's also always calling and texting my boyfriend at all kinds of hours in the day and night. My boyfriend says that how he is and he's not gay but I think differently. When my boyfriends and him are hanging out alone he always send me snapchats of his hand on his back with kissy face emojis, of his private area and his butt. I don't understand why he does that. I think he's in love with my boyfriend. What should I do to fix this ???? Help