i think, IIRC, marriage was made up by the religions because the religions were made up by the tribal leaders way back in the day to control the people, before marriage everyone was humping everyone else and there were bairns popping out left right and centre and not enough food and reqources to go round. when the leaders saw this they though “****, were gonna run out of resources if we carry on in this promiscuous lifestyle” though it probably sounded more like, “ugh , no food, ugh, too much shagging, ugh, stop it” so the religions were created to control the people and marriage was created to stop folk going and putting it about all over the shop, one partner, less bairns(at least thats the theory). over a few years (say a few thousand) it has evolved into the wierd and wonderful thing that everyone is stressing about now.
in the end, if you love someone, who cares? just stick it to ’em 😀 ( but only if its consensual).