Jupiter Hill - The horny sister-in-law

I'm a 36-year-old married man. My wife is 34 years old and we have a little daughter aged four. Since the birth of our daughter, our relationship has been kind of a worm in the middle. My wife Stefanie has somehow developed a protective instinct. She wants to save everything and everyone and give advice. Preferably me and the rest of the family. She has a younger sister. Antje is 31 years old and became a mother 10 months ago. She and her husband Sebastian have also had a little daughter. From my wife I know that Antje's marriage is also in crisis. The two of them are soon talking on the phone every day and they also meet once a week. My wife always claims that she can keep any secret, but she doesn't keep anything secret from me. Sometimes I don't even want to know, but she tells me almost everything. Now to our problems, or rather my problems: Shortly after the birth of our daughter, Stefanie began to approach her environment in a very different way. She questioned everything and everyone. Above all she was very interested in the emotional life of her fellow human beings. Instead of sex, there was always an open and honest conversation in bed. She could not think of anything else but the state of mind of our friends and relatives. The marriage of Antje and Sebastian was her motto. She claimed that she had convinced them of the marriage. Maybe she also encouraged them to have children.