My sister the spinster

Long story short my sister Helen had boyfriend from the age of about 12 and they like they joined together. But David died at 17 in a car accident and that left Helen devastated and she never really got over David. I'm Gordon her only sibling and older by 2 years and I went to university done well and married after and started my career. Helen also went to university and done well, but never dated or seek a new boyfriend. At the age of 38 I got divorced and my ex wife got our 2 children and I pay maintenance and I'm doing very well in my career, even with the maintenance payments. I lived alone until Helen got a transfer to my city and was to stay with me until she was settled enough to find her own place. That was at the end of 2019 and Helen was still not in any relationships and was a spinster. She went to work and done little shopping on way home and stayed home, till she went to work again. Quiet as the dead she was, barely making any noise at all. Spending her time reading or on her laptop, I would go dating or out to movies or sports games and had a quite busy social life. Then the pandemic hit and we in lockdown together, not that it changed Helen's routine much. Except for go to work, but she could like me work via computer from home. Ordering whatever we need online, over the following weeks boredom became a big problem for me. I started to drink a bit more than before, I had to masturbate and watch porn to satisfy my sexual urges. Helen I thought wasn't needing to do anything, but one night I heard a moaning coming from her room and thinking she might be ill, entered her room found she was masturbating herself. She was totally shocked by me just entering and catching her. After an awkward silence, I said sorry I thought you might need help and came in to help. She responded by saying you thought I need help and came in to fuck me is that why you came in. No no I replied I heard moaning and thought you might be sick and need some help. Pity she said I could use a good fucking and I was shocked again. But recovered quickly and decided why not and told her if her still wanted fucking I would be glad to help. She just nodded and so I undressed and joined her in her bed and fucked her and stay the night with her. We fucked again in the morning, sex became so regular for us after that we started sleeping together fulltime. By the time the lockdown finish, Helen had got pregnant as we didn't use any protection at all. Helen after being confirmed as pregnant, got all the tests and the everything showed the baby was healthy. Helen still lives and sleeps with me and our baby daughter Katherine after our mother was born in April. As far as the family knows Helen had IVF.