My computer died and I have to wait a while before I can get a new one so I'm using that time to do research, play with different ideas and ponder over the things I'm working on.
If you're familiar with my AO3 account you may have read "Our Hearts Together, Hand in Hand", an AU to my major story "My Soul and Yours". The idea is fairly simple: it's "My Soul and Yours", only homosexuality has been fully decriminalised and LGBT folks have been granted marriage rights (within countries that belonged to the League of Nations). So, predictably, Feisal proposes to Ned Lawrence, they get married and become co-rulers of Iraq. And I just couldn't help but imagine the impact the new laws and Ned and Feisal's example would have on society.
So here goes, in no particular order:
Acceptance for LGBT folks would grow.
There would be more representation of LGBT folks in politics, literature and the media.
Ned and Feisal are quite a tactile couple. You won't catch them snogging in public but a kiss on the cheek or hand or Feisal offering Ned his arm when they're walking is pretty standard for them. That wouldn't go unnoticed and I wouldn't be surprised if it encouraged people to be more affectionate with their partners.
The legalisation of homosexuality and gay marriage would likely open up a marketing niche for relationship advice books, "marital anatomy" books, other marital aids and so on.
LGBT cafes, clubs and other hangouts that used to be underground establishments are now perfectly legal and mainstream. And it's becoming more and more socially acceptable to be seen there. Ned AKA Lawrence of Arabia AKA the Prince Consort of Iraq being seen in such places will certainly help too.
It becomes necessary to rethink and reform other laws related to married couples. Straight couples benefit from that too. Women in general benefit too.
It becomes necessary to have a discussion as a society about gender roles and the roles of spouses. Straight couples benefit from this. Women in general benefit from this.
As other people in positions of power (royalty, aristocracy, high ranking politicians, diplomats and soldiers) are coming out and marrying their partners it becomes necessary to redefine the role of consort, first lady/first husband etc. All those people are looking to Ned and Feisal for inspiration. They can see that Feisal is treating Ned as his equal, that he's not pushing a complementarian relationship. They can see that while Ned has a preference for "soft" things like supporting education and the arts he is also a very capable diplomat and is not afraid of hard work.