In Skyrim all of the romanceable characters are player sexual. Not sure if it's possible to romance / marry more than one person in a playthrough without mods though.
In Fallout New Vegas you can take both the perk that unlocks extra 'flirty' dialogue with female NPCs and gives you bonus damage against women, and the perk that does the same thing regarding male NPVs, and roam the wasteland flirting with everyone you can and doing bonus damage to everyone.
In Stardew Valley the romanceable characters are also all player sexual. And you can break up with / divorce characters and get together with someone else in the same playthrough.
Also, it's been many many years but I seem to remember Fable 3 being pretty open with your possibilities for romance. In fact Fable TLC as well. You can marry both men or women and take multiple spouses lol.