Advice?! Should I just not do anything? Am I weird?

I'm a 22m if it matters. So the other day I was on Facebook just doing to usual browsing looking at memes and all that when I see that one of my cousins who I haven't really spoken with in a long time adds me. I don't think much of it besides a "oh hi there". Then I click her page to see what she's been up to and see she has a girlfriend and in one picture I notice there's this guy who is pretty attractive, once again I don't think much of it until I see later on she uploads some pics of her and her girlfriend just hanging out along with this guy and I'm here again like "there goes that cute guy". So I don't know this guy at ALL and I messaged my cousin a casual hey how's it been and she's left me on read (she was partying at the time tbh) but I kind of want to get to know this guy but idk how to approach it or if I should just let it go completely.