The way you have phrased this questions makes us wonder if you are not already trying to create a good excuse for ending this marriage. You speak of the marriage as though it were an independent object that 'simply isn't working out,' like a new car. We can assure you, the marriage is not the problem. As is always the case, the problem is in the people. Someone is being immature and self-centered.
The Bible provides no basis for divorce. Jesus Himself stated, 'What God has joined together, let not man separate' (Matthew 19:6). Only God has the authority to end a marriage, and the only way He ever does so is by the death of one of the spouses. So if divorce is not an option, then we suggest that this couple immediately seek out qualified third party intervention. Repairing this relationship must become their highest priority. There is no only option.