“Is there anything going on between you two?”
You're walking to lunch with a coworker who you're friends with. You pass by a woman who works with you. You say hello to each other but your friend and the woman act strangely. You wonder if they're secretly dating each other. You ask him about it.
Is there anything going on between you two?
When you think that two people are dating each other, flirting with each other, or romantically interested in each other, you can say that "there's something going on between" them.
Of course, the phrase "there's something going on" can mean a lot of different things, but when you use it to talk about a possible couple, people know that you mean romance, attraction, or sex.
You can group two people together with the phrase "you two". For example:
Hey, can you two help me carry these?
I haven't seen you two in forever! How've you been?
You can also say "you three", "you four", and so on.