now normally i would not condone this behaviour and feel for the girlfriend, but the fact that she is just his girlfriend is relevant. i want to tell you this story: a very best girlfriend of mine was living with her boyfriend for two years and was feeling really trapped and unhappy. she loved him though, he was a great guy. they just weren't compatible for the long haul. she met this guy at work who was engaged to his girlfriend of 8 years. he was not happy either but loved his girlfriend, he didn't want to shatter her world by breaking off the engagement. he felt trapped too. him and my friend became friends at work and there was a crush there that grew for over a year. they did not sleep together, but they did finally tell eachother that there was something between them that couldn't be ignored. they both broke up with their others and it was a painful process, but was done with dignity and honesty so who can deny them? they are now happily married, have been for 11 years and have a beautiful one year old daughter. i would have never told them not to be close if i could see the future and what they were to eachother. my advice to you is be his friend, do not i repeat DO NOT engage physically with him (IF HE TRIES THIS BEFORE WORKING OUT THE GIRLFRIEND STUFF HE IS A CAD AND SHOULD BE DROPPED.) and maintain a sane mature level of friendship and honor. he may be yours should you want him.