My wife's Sister

I'm Wallace 32 married to Rita 30 and we have 2 children. Rita only has a sister no brothers and her sister Briony 35 is a lawyer and doing quite well in her career. But not in her love life. Briony is overweight and wants to have her own child, Rita knows how badly Briony wants a child. So she decided that we should help Briony as we live side by side in our own houses and Briony looks after our children when we goes out on a special evening together. Without asking me first she put her idea to Briony who was a little unsure, but Rita convinced her. Then and only then she asked me, as to her mind it was a done deal. But I was all that willing at first, but wanting to keep my sexual privileges with Rita I agreed. Leaving to how and when up to her and no more heard for several weeks on the subject from Rita. She had run into a wall on how she thought it would be done. A turkey baster and me masturbating was her idea, but the more she checked on it. The more uncertain she became, then she finally decided on straight intercourse between me and Briony. She knew I wouldn't be willing or would Briony be willing on straight intercourse on our first hearing of it. But she worked on us both and with me said it would be a threesome and after some more arm twisting as they say I agreed. Briony was still unsure, but agreed also and then it was all up to Briony's circle. On the chosen evening and the children in bed we had our first threesome and then another and then another. Finally Briony got pregnant and so did Rita as a reward we had sex after I had fucked Briony. So now it was the normal routine for us when Rita was pregnant, except Briony was also pregnant. Both babies tests were fine and Briony was delighted to be having a daughter and Rita was having our second boy. Last month both babies were born healthy and only a day apart. Mothers and babies are doing great.