Commitment and Oneness are the twin pillars of marriage. I know there are people that have written about many more 'pillars' in marriage. I think these two cover most everything.
One might well ask, "what do you know about it? You've never been married. You're gay."
These are valid objections. Experientially, I know nothing. I do know what I have observed. I know what I have read in God's Word. I am well aware of what Jesus and Paul said regarding marriage and divorce and the things that would justify divorce. What I find is two things. Sexual immorality or more correctly, sexual activity outside the bounds of the marriage covenant or the desire of an unbelieving partner to leave a believer are both seen as valid reasons to allow divorce.
Let me state up front that God hates divorce. He always has. But He also loves his people. When a sexually immoral or unbelieving partner wants to leave the marriage covenant and it appears there will be no resolution to that situation, God will accept that divorce for the sake of the believer.
No married person should have to accept infidelity or the confusion of their partner about their sexual identity. If the situation cannot be resolved, there comes a time where a decision must be made. The victim of this wavering mate must at some point decide to move on and allow their marriage to dissolve. Release will bring renewal to the one and force the offender to make choices and decisions about the direction of their life.
I say this knowing that both parties may still love each other in some fashion. They may both fear the loss of security that some think comes with being married. To this I would say that the division does not have to be acrimonious. Many divorced people go on to be friends and share in the joy of their children and grandchildren. They become friends rather than marriage partners which may be what they should have been all along.
There are many motivations for marriage. Sometimes it's sex within the bounds of God's will. Sometimes it's partnership and friendship and children with sex as a side benefit. People have different reasons to merge their vital interests. Some simply want children.
There are same sex attracted people that will marry only because they want children and they want to be able to operate and appear in the straight world as normal. They use their mate and family as a disguise. This is a gross violation of the two pillars. It is deception. It is manipulation. It is hateful and it is cruel. Those that do this often do not see it that way.
To those that have done this to their partners, I say repent. This will not be an easy process, but you need to get out of the secret activities and break the habits that will eventually destroy you. This process could take years. You will probably fail along the way. This is why you must rebuild your relationship with Jesus and understand that His well of grace never runs dry. If you have left the church, then go back. You may not want to go to places openly hostile to people like us. You will need a place that understands that we are all sinners; a place where you will receive unconditional love for your repentance and desire to turn away from the sin that seems so natural. It should be a church that will support you in some way with your struggle. Most important, stop using people for cover and for sex. It is duplicitous at best.
To the partner victims I say divorce and take every last crumb in the cupboard with you; you deserve better. Let God deal with the user you married. In some regard, this seems harsh, but enabling the user is not a good thing either. If you still love them, this might be the best thing for them.