Of course they can. At various times in my life I’ve had best friends of both genders that I never ended up romantically involved with. We were great friends, but just not interested in each other in ‘that way’. Friendship comes about from common interests, common experiences, and a meeting of minds. Sex and gender have nothing to do with it. That doesn’t mean that friendships never change into romance, but that doesn’t always happen.
Romance pretty much requires some amount of friendship to succeed, but friendship doesn’t require romance. The same is true for romians or monians. Anytime its possible for two people to be romantically involved, it’s still possible for them to be friends without any romantic or sexual desire. It doesn’t matter if they are a romian man and woman, two lesbians, or two dorians it’s always possible to be friends if you have enough things in common.
The main difference about this type of friendship is that all the people involved need to be secure with themselves. Not only the friends themselves, but any partners they have. Actually insecurities can always cause problems in any friendship or relationships. If you have an insecure lover, they may be jealous of your friend if they think they could be a threat. If everyone isn’t secure with themselves, then you will likely end up either losing your friend or losing your lover. I don’t like jealousy, so I usually don’t end up with people in which it becomes a problem.
Note: If you don’t know what romian and monian means go visit http://iwantmygayback.com/index6.html