Hmmmm, why not keep it simple and start with defining a friend. To me a friend is someone you care about who cares about you. Someone who tells you when you are wrong and supports you when you are right, etc. etc. Add living together and sex and you have a boyfriend. I don't believe the sex has to be monogamous, but that is up to the two people to decide. I have been with my BF for three years now and do to our age difference I offered him an open relationship. Surprise he wanted monogamy and so far it has worked out well for us, but each to his own.