Been thinking about this for awhile and romantic ideas that involve sex between characters can be just as fun as non-con ideas with sex between characters.
Now for my current cravings for romantic based plots:
1) Empty House
Happily married couple has house to themselves for first time in many months. Kids are away somewhere but will return in about 36 or 48 hours. It's time to make up for lost time and who cares if someone can see what they are doing with the house to themselves.
2) High School Reunion
They were high school sweethearts but things happened and now married to other people they haven't seen each other in nearly 20 years. By the time the reunion weekend if over, they will be heading out of town to start over as a couple and the spouses they leave behind will actually cry because of the happy ending for the sweethearts.