It was expected to get married and sire heirs. You didn't have to love your wife, you were more then likely married for political/territorial reasons. The wife ran the household, you visited her maybe once or twice a year, did your duties sire heirs and offspring to continue the name/clan/familial lines... and then went back to what ever it was/who you were doing.
It was common for an older male to take a younger male under his wing to mentor, and that did include sexual activities. It was practice for the younger one to submit to the older. The Spartans did this quiet well with the warriors and the trainees.. not to mention the Athenian intellectuals, and the Macedonians.
Was Alexander the Great Gay? In our modern day terminology, probably yes.
In the ancient terminology..? who knows, he was doing what his society does, and it was acceptable then... especially being in the military and bonding with his fellow man. It was common and accepted. It is hard to put modern day morals and sexual repression or terminology on an ancient culture who had different societal and cultural norms then our time.