There is a temple worthy couple named Ty Mansfield and Danielle Palmer. Both of them are faithful LDS members, he co-author a book about homosexuality and how he left this lifestyle to serve the Lord. Now, Ty (a family therapist) admits he is gay. He is open about it. Danielle knows it but despite this fact, both of them decided they will get married.
He said the following:
Sometimes I read things like this and it just spins around my head how they make it work because marriage in itself has many challenges. I don't see how you can also be "openly" gay but still want to marry a woman? Strange.
Gay, Mormon and Happily Married with Children
Josh and Laurel "Lolly" Weed seem to have it all -- three beautiful kids, a wonderful home and a deep and unflinching devotion to their Mormon faith.
But on their tenth wedding anniversary this summer, they decided it was time to unleash a secret so sensitive, so personal, they weren't sure what the church's reaction would be. Ref. Source 4
The Mormon women who married gay men - and they're all fine with it
The mood lightens when a cute male server approaches the table to take their order. But it's the husbands - not the wives - who start to flirt with him, suggestively joking that he milk a goat by hand to make cheese for their salads. Ref. Source 4
This is different than if you married the person and then they decided to reveal their true sexual orientation after. In the case where the person openly says they're gay but you still marry them then you are walking into a world of trouble. Marriage takes a lot of work and having issues from the start won't help.