How do I approach my cousin w/this?

Hi ladies so my cousin and I are so close, I love him to death. We’re around the same age (25) so we’ve gone out a couple of times, he’s met my friends and vice versa. He’s actually messed around w two and I never cared, I just told the females not to include me in anything that has to do w him.

Now years later roles are reverse. About 5 years ago I met one of his close friends, we’ve always been attracted to each other but we were doing our own thing (in relationships) so I’ve never been out or did anything with any of his friends. Recently we all hung out (now we’re both single) and we were flirting the whole night and did kiss. At one point I called my cousin to make sure he got home safe with his friend. (He was drinking, but his friend drove them) and he goes “______ better not touch you” I started laughing and ignored it. We’ve been texting and he inv me to his house this upcoming weekend for his birthday and he just told me he invited my cousin. I just don’t want my cousin to feel any type of way, I don’t even know how to approach him? I just want to make sure he’s okay with this.

I just told his friend that what happens between us stays between us because I know how much my cousin values their relationship and I wouldn’t want him to ever feel like he’s in the middle & he agreed.

So how would you approach this??