There are many stories in the 4th aliyah of Parshas Vayeira, and they all have a common element. After Sodom is destroyed and Lot is saved, he has children with his daughters. After Sarah is taken by Avimelech and he repents, Avimelech is able to have children, and Sarah gives birth to Yitzchok. All of these children are born through different relationships. We learn about the different aspects of relationships in terms of genuine chessed, true giving and expansion of oneself, and chessed meaning shame, a lustful relationship that is self-serving. We want to access the chessed of Avraham-true giving and expansion of self-which is the antithesis of Sodom.