Securing my future

I married my husband four years ago; I was 30 and he was 57 he wanted another child. His only child a son was weak, and he thought to be gay. His son (then 17) took after his late mother and was very smart and avoided sports, preferring to study than play sport. My husband's health wasn't great when we married. But in the four years since it had gotten much worse, now unable to get a hard-on or even stay awake. Long enough to fuck me with me doing all the work. His son now 21 and at college, was still gay as far as his father was concerned. I knew his son wasn't gay by my observations of him, he was very much into girls, but too shy to approach them. I'd even caught spying on me changing several times when home from college. But hadn't let on I'd seen him, mainly for fear of giving him a bigger complex than he already had. My position in the family was more nursemaid to my ill husband than his wife. Unsure of my future if my husband was to die, there is a prenup, but that mentioned providing a child. But didn't actually state by my husband, just to carry on the family name. My thoughts on it were if I was to get pregnant via the son, I would be still honoring the agreement. But my stepson was very nervous around female his own age and only relaxed with mature women closer to his father's age. I decided to seduce my stepson during his next home visit, how was easy catch him spying me and take from there. I was sure he would spy on me as he had before, because I pretended not to see him. Fortunately, his father had a turn and was in hospital for a few days over his son home visit. I duly caught my stepson spying on me undressing, after visiting my husband at the hospital with my stepson. He was very nervous about what I would do after catching, fearing I would tell his father who he feared greatly. I believe if I did his father would be overjoyed by the news his son liked looking at women. So, I made him sit on my bed and watch me finish undressing, he got a hard-on and it made a bulge in his pants. I told him to join me in my shower; he followed me into my bathroom like puppy. He was so nervous he was going shower with me fully dressed. I'd to undress him myself, I fucked him in the shower also and then in my bed. After which he returned to his room, I awoke early and decided to fuck my stepson again and so I went to his room and fucked him. I fucked him every chance I could during his home visit, even after his father got out of hospital. I think I was lucky as I missed my next period and the one that followed before getting tested. I was indeed pregnant, but how to inform my husband I was pregnant. He would know it wasn't him and might divorce me straight away. But he relapsed into a long coma (18months) and would never recover consciousness. By the time of his passing, he'd a granddaughter named after his late wife who was one on his passing. His son home visits were sexual as he was quite comfortable around me since I started our sexual relationship. I was quite happy to continue sexual relations with him as would be inheriting soon rather than later. We really got it on the night after his graduation and I got pregnant again. Not needing to work due to his inheritance, we moved to east coast and set up house together. We haven't married no real need I'm the mother of his children and his sexual partner. He is still nervous around younger women; I see it as my duty to provide sex to him as long as he wants me too. Also, I don't any precautions either I think it better if I keep providing him with children as long as I'm able too. Sort of fulfilling my agreement with my late husband, providing extra heirs.