I stayed with my grandma

My grandma Tracey 65 widow and lives in a small town, I had returned from years working overseas and was asked by my mother Gwen to stay with her mother Tracey and help her. The pandemic was ramping up and Gwen was worried about Tracey being alone. I agreed and arrived just days before a lockdown was called. We stocked up just before everything closed down and I worked on Tracey's yard and house doing minor repairs. I'm Dave 24 and of stocky build and do okay with girls. But no one special even now, being lockdown with just Tracey around I tried to keep busy and didn't think about sex all that much. But my mind wandered into sexual thoughts now and then. On the whole I would put them out of mind quickly, but several times I had to masturbate to release the tension. Then one day I came inside and caught Tracey masturbating herself on her bed. I got an instant hard-on. On her seeing me watching her and the bulge in my pants she asked me to join her on her bed. We had sex and it was the start of regular sex between us. After the lockdown was over I stayed with Tracey and my Gwen came for a visit. Gwen hadn't ever married and my father cleared off once he knew she was pregnant with me. I've never met or heard anything from him all my years. Gwen 41 and soon realized that I was fucking Tracey and wanted to join in with us. She sleeps with me every night and has threesomes with Tracey and me. She lost her job when the second lockdown started and we are all living and sleeping together still.