Promise to my wife

I've been married 8 years and we have 3 children and are both in good careers. In early 2020 I asked by my wife would I do her a very big favor. I said I promised to love and care for you at our wedding, so of course I'll do you any favor you want. Then she stunned me asking me to get her cousin pregnant. Her cousin hadn't found her perfect man and time was running out if she was to have a child. Her cousin was 3 years older my wife and 1 year older than me. I had agreed, but thought it was a trick or something. It wasn't they had concocted the idea and after dismissing other ideas. The main reason they chose me, it would link the child to my wife and me. Just in case something happened to her cousin. Her by her cousin and me being the father, anyway I had already agreed and so I just made 1 demand before her cousin moved in in with us. Threesome, fucking her cousin with her in bed with us. She said that was the whole idea anyway. So, we fucked for several weeks, and the cousin just got pregnant before the lockdown (2020) was imposed. All able to work from home it didn't cause much trouble to our lives. The main thing that happened was I got my wife pregnant with our third child during the lock down. The cousin had a daughter, and my wife had a second boy, and her cousin still lives with us. She is also pregnant again and my wife wants her to live with us after the birth of her second child as one big family. I'm quite happy to have her staying with us, as I'm getting regular sex from her as well as my wife.