Looking for one or two ladies for a mother X son X daughter-in-law love triangle.
Could have a royal or a modern setting. The son has always been very close to his mother, and their love took a turn towards the taboo when he turned 18. Since then he's been so attached to her, that he seems unable to make love to his bride at home, knowing that mom is in the other room. It never had been a problem earlier though when they did it at her place or in the car etc. On the third night, out of sheer disappointment, he confesses before his wife. Obviously, the wife is upset to no small degree. Only the mother can now convince her to cooperate and together they can get rid of his troubles. A pregnancy (or two!) may follow.