I have to agree with others and wonder why it matters to you if he's your ex. What your ex does with someone else is no longer your concern because he's your ex. On the other hand, to answer your question, can a guy hang out at a girl's house and not do anything? Sure, my guy friends come over all the time, we play PS2 and eat Mexican Food and shoot the shit. I have more guy friends than girl friends (I'm not particularly fond of women as friends, they're just as annoying as I am lol)