Chance meeting

I 24 was out jogging and came across my old history teacher 52, she had been jogging and twisted her ankle. I helped her back to her car. I was invited to Sunday lunch as a thank you and I never refuse a free feed. I arrived and had a nice lunch; she caught me staring at her breasts and so removed her top and bra to give me a better look. We'd sex that afternoon; she likes sex, and I became her go to guy for sex. Divorced and not in any relationship herself and as I was quite willing it became a regular sexual relationship for me. I was dating girls, but none seemed right for long-term relationship. Then I met my history teacher's niece, who was also a lover of hers. We had a threesome and clicked as they say, fast forward a few months we married. Not because she was pregnant but because it felt the thing to do. I moved in with my now aunt-in-law as she owned her own home and I'd been renting, my wife was soon pregnant, and threesomes were regular and still are. Perfect relationship, only the three of us know of our sexual relationship. None of my family know about me fucking my aunt-in-law, neither does her family know about us or her long-term sexual relationship with her niece.