The nature of children, their dependence on adults, dictates that parents consciously commit about 20 years of responsibility to their offspring. This long term obligation is part and parcel of whatever value children may represent to the individual. What values could possibly offset this price, and can these values be rational?
There are indeed important rational values to be had. One's children can be a precious metaphysical expression of a perfect romantic relationship. A concretized manifestation of merged characteristics of two people who value each other highly. Similar to the romantic relationship itself, but different in form and expression, children can serve to provide what Nathaniel Branden refers to as psychological visibility. Children's presence in a relationship can serve both as a constant reminder of the admirable characteristics of the parents, who as self-actualized adults value themselves, as well as a symbol of the bond, the integration, of the two individuals' lives. Naturally, children are also individuals and will not always reflect the parent's values. But even this, the expression of individuality and free will, can and should be a value to parents; it affirms their objectivist philosophy and demonstrates their highest value, individual human life.
Most (intentional) parents obtain great value from teaching and molding their children, and from just watching human life, this most precious miracle, evolve and flourish. We can also learn much both through the process of teaching our children, and by understanding their often fresh, innocent perspectives of life. This innocence, as well as children's often uninhibited display of love, can be a valuable source of pleasure, provided that one doesn't become dependent on unconditional love.
There is another, more abstract, value to the concept of family. Human civilization and the highs it has and can achieve are not possible without the accumulation of knowledge passed from one generation to the next. This is to say nothing of the obvious necessity of successful human reproduction without which we would not even be here. Children and family represent in an abstract, sense-of-life manner the importance and value of this aspect of being human. ... Long-term intellectual evolution can be seen as a basic moral principle that enables improved human survival.
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To summarize, there are many values that children may represent to us. The rational choice to have children and the assessment of their value to us must be done in the context of the long term commitment and conscious appreciation of both the pleasures and "sacrifices" raising children entails. The is no guarantee that we will always love our children or that they will love us. By the choice to have children we assume responsibility for their existential and emotional support, their safety and education for the long term. If the projected values we obtain from having them substantially outweighs the negatives, then there is no sacrifice. The fact that there are no guarantees, is no different to "sacrificing" free time or luxuries to a business venture which is projected to be of great value to us. Irrespective of the outcome, we should do our best to get the most out of the building experience. Life is about the journeys as much as the destinations.