I started a harem accidently

I married at 24 and at university and my wife wasn't pregnant at the time. We just decided we were right for each other and so we married. I come from old money as they say, my family have always been very well off and I had no interest in a city business life like my father. I had money already and was studying animal husbandry and planned to live in the country on acreage, same for my wife she was a country girl and didn't want to live in the city, but unlike me she didn't come from old money. Her family owned a farm and were doing okay and so I bought an old farm close to her family's farm about 4 miles away. The house was run down and so were the other buildings, but I didn't buy the farm for them I bought for the land 374acres of degraded soil. But I was still at university and in no great hurry. I had all buildings removed and a new house build as per my wife's wishes and a barn and outbuildings we required. No animals as we were waiting till we finished university. Several months before our graduation another block of land 86acres came up for sale this land was marshy and low lying mostly a few acres of dry land the rest waterlogged. But I saw it as a benefit and had the ground dug out to form a small lake. It also joined our farm to her parent's farm and the lake when full would allow her father to irrigate during dry spells. After graduation we moved into our new house and settled in and my wife's twin sister complete opposite to her, hung out with us a great deal of the time. Anyway, at their joint birthday party we had a little too much to drink and all awoke next morning in bed together naked. My wife and I were trying for our first child, so she wasn't protected, nor was her sister who was still a virgin till that night. Well, you guessed it they both got pregnant, and I wasn't shocked that I had fucked my sister-in-law. But her getting pregnant was at first a shock for me, my wife thought it funny at first and she really loves her sister dearly. They are so, so close and get on very well together never fighting like me and my siblings. Not wanting to get aborted her sister would carry the shame as it were, except my wife wasn't having that. Insisted her sister live with us and become my second wife as she said, my wife was more hands-on farming and prefers working outside and her sister was more housewife than farmer. So, they divided the jobs between them, my wife helped me with animals and her sister would run the house and get assisted by us. Also join us in our bed, so I got a bigger bed. We were setting up a stud and intended to breed bulls and had couple of dogs and chickens and horses to finish off our animals. Her parents accepted it as it was better than being thought of as a single mother and living at home. My wife had me buy wedding rings for her sister and by changing her surname to mine. Made the children she had like brothers and sisters of my children with my wife in name. Now 23 years later I've 12 children 6 with each wife and a set of twins with each. The house was enlarged over the time.