I am wondering about the marriage laws of Westeros. To keep this question from being too broad, let’s discuss only the case of the prevalent religion of Westeros, the Faith of the Seven.
We do know that a marriage of people adhering to Faith of Seven can only be annulled by the High Septon or a council of faith if it hasn't been consummated.
The following orders require vows of celibacy in Westeros:
We do know Ser Quentyn Ball sent his wife to join the Silent Sisters so that he could be free to take the vows of the Kingsguards, since he couldn't get his marriage annulled as it had been consummated. That implies that simply swearing the Kingsguards vows won't automatically annul his marriage.
So what happens if a married man is made to join the Nights Watch? Does his marriage get annulled automatically or is his wife bound to be alone for the rest of her life?
Also what happens if a married man takes the vows of Citadel to become a Maester or becomes a Septon?
For women adhering to the Faith of the Seven, the situation seems clear that joining the Silent Sisters will annul their marriage. It is not so clear as to what happens when a married woman wishes to be a septa? Virginity might not be required to take a Septa's vow because we know Septa Lemore has childbirth marks. (But that in itself means nothing, she might have gotten pregnant after taking a Septa's vows. That is of course if she is not what she is suspected to be).
I have also created a Reddit thread for it here, but there are not really many insights there. But do check it in case there might be some comment which might help you form your answer.