It is nice to play a little nosey parker sometimes like asking people, "Eh, you got how many ex?" Sometimes, it is not the answer that I look for but rather, how the other person reveal.
You know they trust you enough when they tell you things that you don't expect to hear. You know that you have sealed a certain level of friendship with that person because of the way they describe.
It gives you the fuzzy feelings of knowing that you actually have someone who is close enough to talk about certain things.