Living off the Grid

I'm David 37 divorced, I'm a Geologist. Three years ago I purchased a remote property of 450 acres in the foothills of the local mountain range. After my purchase I choose a site on a hill to build my new home. Using mainly local materials from my land, stone for the external walls and fireplace. Local slate for the the floors and lumber from my trees for the frame, doors, shelves and such. The only new materials I got was the double glazed windows, solar panels (including a solar hot water system), metal roofing, plumbing and electrical materials. I sank a bore for water (450 yards from the house) and install a solar pump to pump it to the house, where I had a plastic water tank (2000 Gallons) on a raised platform to gavity feed the water to the house. With inline filters the water is very good for everything. I also installed a reed bed system for the household waste water that overflowed into a dry gully for clean water get away. It took 16 months to get it all finished, including a barn come garage for my 4wd and quad bikes and my 3 horses. I fenced in 2 acres behind the barn and build a chicken run for my chickens. Strongly fenced to keep out predators, I also a vegetable garden planted. I liked living alone away from the hussle and bussle. My ex wife has remarried and I get my 2 children for the second half of the holidays (every second Christmas). They are 15 and 12 both boys, they like visiting me. Nine months ago my youngest sister Robyn 27 came to visit me, after her husband Gary had left her for another man. I always thought he wasn't really in love with Robyn. They had no children and she was left well off by the divorce. Robyn isn't the brightest, a lot like Kelly in "Married with Children" TV comedy. Anyway after she had been visiting a couple of weeks, I came home from work and she was nowhere to be seen, so I started to around for her. I walked down the hill from the barn to check the little pond I had made by damming a small creek about a mile from the barn. As I came upon the pond I could see Robyn swimming around and she was naked. I stood for a few minutes just looking at her body. Then I called out to her and she stood up and just walked out of the pond, not trying to hide anything. I asked her "What she wanted for dinner". She replied "Anything would be fine", so as we walked back to the house. She hadn't even got got dressed, only putting on a pair of sandals. On arriving at the house I suggested that we go into town for a meal and a movie. She agreed and she went for a shower, I said "When your finished I have a shower and then we can go". She said "You can join me and wash my back", I replied " I don't think that would be right". She responded " Who going to know and I would like you to wash my back. Please". So I joined her in the shower and washed her back. I got a hard on and it was touching her ass and she pushed against it saying " Stick it in, I need a good fucking". I didn't do anything and she said " Go on fuck me, I really want you too". So I did and after we went to town had dinner and seen a movie and returned home and went to bed together. We have been sleeping together ever since and she is pregnant. Only 4 months, she had told me that she wanted me to get her pregnant. But I had resisted for a while, she told the family that she had a one night stand with some guy and she got pregnant. My mother wanted her to go to home to her. But she said she wanted to stay in the country and she would okay and that I'm around.