Both Divorced

I've only a sister 47 and both our parents have passed away in 2020 due to Covid. I 49 have 2 grown children who have their own families now and don't visit me much at all, nor their mother my ex-wife much as well. My sister had two children and one died, he was in a car accident 2021 and the other has her own family now also and likewise like my children in visiting her not much at all. My sister and me both live together in our parent's old home, which we inherited on their deaths. As we were divorced before their deaths it made sense for us to live in the family home. Being together most of the time and neither dating either, we became very close and a lot closer than we were growing up. Neither of us are anything special in looks but are fit as we go to the gym 4 times a week and jog about ten miles on each of the weekend, unless it's raining. Swimming is another exercise we do at the local lake in the Spring and Summer. It was while at the lake we started getting amorous and feeling each other up. But that was all we done, but we left earlier than usual and once home. We were still amorous and behind closed door took it all the way. Now fulltime lovers and sleeping together every night except when we've visitors, which isn't that often. We act like we're a married couple not brother and sister. My sister wears our late mother's wedding rings, she had given hers to her daughter. Not many people know we're brother and sister as there is a great number of new residents in the area since we left to marry and start our family. Those that do are in their seventies now and their numbers are decreasing every year. We aren't active socially with many people locally either preferring to keep to ourselves. The sex is mainly for our mutual benefit and of no concern to anyone else.