Now a more realistic scenario, A1 and A2 are married at least in respect to performing the outward actions in respect to church teaching (wedding in church etc.), three children. A1 and A2 were if to be put in a box agnostic prior wedding and some time afterwards with A1 having been raised as cafeteria catholic. Children not baptised.
A1 decides one day “Upps, being an agnostic is such a stupid error, realy sorry for that mistake, better try being a catholic”. A2, considering the catholic church to be a misogynic, child-abusing, hate-filled criminal organization being guilty of fighting enlightnment, women’s right and modenernity with torture and murder, is somewhat displeased at the decision. After some nice discussions spanning over a few months covering interesting topics like divorce, “you are endangering my children by taking them there” (meaning mass), “why cant it be protestants? they are not that criminal”, “they brainwashed you, but they will not have my children in their evil claws”, “And what about my brother and your sister? They are evil now for you?” (both being homosexual), “you hurt me so much by going to church” a somewhat unstable armistice about the issues is formed with A1 sometimes gaining permission to attend mass with the children (though baptism is still a no-go area).
If the brother of A2 would now decide to “marry” his homosexual partner of many years, how should A1 deal with the problem that saying to A2 “Sorry, you can go, but i won’t and the children shouldn’t attend either” might be interpreted by A2 as a new declaration of war with the consequence of a new round of interesting discussions? With more or less silent dissent attending the farce, especially the permission to take the children to church sometimes would not be endangered.