Started new life with my Cousin

Widowed in 2019 car accident and so moved back in with my mother (72), she was frail and not in good health. I'm now 48 and back in late 2022 my cousin David now 50 moved into the area to restart his life after passing of his wife due to cancer. David bought a block of land just outside of our town and set about building a home for himself. On rise on his land, he dug down to make a basement, using the dirt to make a pond between the house rise and the next rise. His house was all on one level no counting the basement, his house windows were at the front and back of the house the sides were solid concrete with earth banked up against them. It looked like his house was built into a small hill, after it was finished with a large patio overlooking the pond. It looked great and as he had 4 bedrooms it solved a problem for me and my mother. Our house in town had the bedrooms upstairs and my mother couldn't cope with the stairs anymore so was sleeping in the lounge room. David thought it would be better for us to live with him as everything his aunt would need was on the one level, even the garage. So, I could wheel my mother to the car no steps to negotiate. My mother thought a great idea and so sold her house and split the money with me and my two brothers. My mother like sitting on the patio looking at the view and the birds using the pond. That was May 2023 when we were settled in, it made my life easier looking after my mother and gave me more time to myself. As a result, I got closer to David and finally after my mother was in bed asleep, we used his hot tub another favorite thing of my mother. Without asking David kissed me, I was a little bit shocked at first but kissed him back anyway. Well things developed from there; we ended up in his bed fucking. After our first fuck I realized I needed the monitor I'd left it on the patio. Checking on my mother first, while David got the monitor we went back to his bed and continued fucking. I started sleeping with him every night, even moved my clothes into his room. My mother knew nothing of our relationship and still doesn't, I'm passed having children and mine only visit for a day at a time, David's children likewise. David upgraded his car to a transit van, fitted out to take his aunt and me in comfort. On my mother's stay in the city hospital, we stayed at a nearby motel same bed. We could've stayed with David's daughter and her family but said we've to be close to the hospital to cover our motel stay. Nobody knows of our relationship, David's mother was my mother's older sister, but she passed away in 2016. They have always been close David and my mother and so it wasn't a huge surprise he moved closer to his aunt to restart his life after losing his wife. If we could marry, we would even our children think we're like a married couple and probably think we're passed having sex anyway.