Diana Gabaldon touches on it in her Oulander series.
There is more obvious senario with one girl and two men. I don't think it appears until the 3rd of 4th book (each over 900 pages), but it is mentioned over the course of a couple more books. A girl falls in love with twin brothers.
She spends much more time developing the relationship of a homosexual military officer and the main character, who is VERY straight. It shows thier friendship and love develop even with no sex and how the main character's wife deals with the knowledge of the officers feelings toward her husband.