Have You Ever Seen The Movie The Big Chill?

You know that part where the wife tells the husband to go upstairs and give their friend what she needs for a baby? Well, I got to live that dream with my wife and her sister.
One weekend I am having a completely normal Saturday when my wife out of nowhere tells me to follow her into the bedroom, I know I am not getting lucky because the kids are here so not sure what is going on but I follow her in there. She says I am about to ask you do something that I know you are going to say no to but I really want you to do it for me and for her. I am standing there dumbfounded as hell and ask Do what and for who?
She gets done explaining herself in like a minute and she was right, I was standing there thinking no way she just asked me to go to her sisters place under the guise of something needing repaired and fuck her brains out. Well to be honest she used different words but that was what I heard. I tell my wife that things could get real complicated with doing this, what about responsibility for the child should this work, what about this and that and my wife just looked at me said Are you going to do this or not?
I drove over there thinking the whole way that this was a set up, wife was testing me to see if I would cheat on her, there was not going to be any sex just me getting yelled at then divorced. I kept going though and arrived at her place and went up to the door, did not even have to knock as the door opened up and she invited me inside. She thanked me for coming over, told me I was amazing for doing this for her and I again asked her about the same things I asked my wife, her sister. She told me not to worry but also mentioned that these things do not always work the first time so was I willing to do it multiple times over the next few days because she was ovulating. I ended up putting three into her during our first ever time making love, or more accurately having intercourse.
I tell you what the first one was about as romantic as a fishing trip with your buddies, she literally got up on her bed doggy style and told me she was ready for it while this long dress night shirt thing was flopped up on her back. I came up behind her and got hard just from all the excitement of it, she was quite wet though and I came after probably five minutes of doing it because she was tight as hell and I was turned on a lot.
when I came she went down on the bed rolled over onto her back and lifted her legs up telling me the doctor told her this was a good thing to do after ejaculation. I felt like I had just completed a lab experiment standing there with my cock out still damp from her pussy looking down at her in a yoga position with her pussy still exposed. I gave it like a minute and asked if she was ready for another one, she looked up at me and said Really? I pulled her back to the edge of the bed and pushed her legs back spread them, had it hard and in her in a few minutes and lasted much longer that time even hearing moan and gasp a few times. I tried giving her oral when I was done figuring she would want an orgasm but she told me No, they told me not to have oral sex because of the saliva. I told her she had to be a little frustrated not having an orgasm and she just looked up at me saying she did have one, I was surprised by that and said Okay, well I will do whatever you need me to do and she said that two was enough for now but could I come over around eight tonight for more. I told her see you then and drove back home after having the strangest sex of my life to date.
I get home and my wife is looking at me a little surprised and this little smile goes across her face, she pulls me into our bedroom again and says So, how did it go? Did she want you to go thru it still and mentions she did not expect me home so soon. Second strangest conversation of the day as I told my WIFE that I put two loads into her SISTER and she wanted me back later on for more. FUCKING I did not say out loud. My wife was happy about it, turns to me and says you know what? we should get pregnant again so she has a cousin the same age. I am standing there thinking this is just fucking crazy as my wife is already calculating out her next ovulation in her head. She literally walked out to the kitchen where she keeps this calendar on the side of our fridge and points to this date on it, looking at me and says these three days right here. Let's do this and gives me a big hug and kiss. So four months later after three sessions with my sister in law and two with my wife they are both pregnant, needless to say her sister thought it was also a great idea to have two the same age also.