Incsts Wife

My wife and I have always been very open minded about everything. Our relationship, sexually speaking, has never been exclusive, and we have told each other very profound secrets.
From my part, one of such confessions was about a special relationship I had in my youth. I had a sexual, incsts relationship with one of my cousins. We were about the same age, fell in love and lost our virginities to each other. We kept our relationship going for a couple of years in secret, we even called each other "my love" in private. It was a very deep connection that felt very natural despite the taboo, that tragically ended when she died shortly after.
I confessed that to my wife one night, not knowing what would happen a few days later. She opened up about having a very similar relationship with her own brother, since they were both teenagers. They were deeply in love to each other and were sexual partners for many years, well into adulthood. She explained that, for the most part, they only dated other people every now and then for the sake of appearances. She claims they were each other's one true love, but were painfully aware that they could never be together in the long run.
Then my wife met me, and our connection was too strong. She said her plan was to date me for a while and then dump me, but she genuinely fell in love with me. As soon as it became serious, she chose to talk to her brother and end the sexual side of their relationship. It was painful for both of them, but he understood. I wouldn't have suspected a thing if she hadn't told me: he was always very warm and receptive of me.
Her confession took me a little by surprise, but I could understand her. I knew, given the non-exclusive nature of our relationship, that she would ask about seeing him and having sex with him again. It was uncomfortable at first, but I agreed. Our sexual life only benefitted from it. It was already great, but now she seemed much more fulfilled and happy.
Things took an interesting turn the first time us and her brother got together after our new arrangement. The topic came up, we talked it out casually, and concluded how deeply in love we both were with our wife. That night, we ended up making love to her together.
We have a new arrangement now. My brother in law moved into our appartment building, only a couple of floors apart. He has the key and maintains it for appearances, but for the most part, we lives in our place, which is bigger and has a room for visitors, which we have outfitted with a big bed. Sometimes, my wife spends the night with me. Sometimes, with her brother. Sometimes, the three of us sleep together after fucking. As forbidden as such a taboo is, it's a wonderful arrangement. My wife has never been happier, and we're both deeply in love with her.
A couple of years ago, she gave me a child. Now she's expecting a child for her brother. For legal reasons, they'll both be registered as my kids. But her incredible love has made her a mother and wife for both of us.