Hi! Try these:
http://www.mangago.zone/read-manga/kekkon_suru_kamoshirenai_otoko/
http://www.mangago.zone/read-manga/kekkon_shite_kudasai/
http://www.mangago.zone/read-manga/okusama_ha_alpha/
http://www.mangago.zone/read-manga/ookami_he_no_yomeiri/
http://www.mangago.zone/read-manga/until_i_meet_my_husband/
http://www.mangago.zone/read-manga/the_crows_marriage/
http://www.mangago.zone/read-manga/kasegimasen_kara/
^ Super shoujo manga-like
http://www.mangago.zone/read-manga/mother_s_spirit/
And that's about what I got from this tag:
http://www.mangago.zone/tag/marriage/
I know that there are a lot of marriages happening in the BL world but those are mostly Omegaverse. There are a few mangas that feature marriage overseas in a country that allows same-sex marriage sprinkled around.
i want a yaoi where they get married