My wife's horny sister

We had built a two-family house. The first three years we rented the upstairs apartment to an older couple. When the husband died, the elderly lady found a smaller apartment. Because my wife's sister, her husband and the two girls (17 + 19) were also looking for a new apartment at that time, they moved in with us as the next tenant. My sister-in-law is with her 39 years and a super, no a simply h...