"Nothing, absolutely nothing, compares with the companionship between a husband and a wife. And nothing, absolutely nothing, can provide the joy and growth that come from happy children who make a family circle. Throughout my life, I have answered to many titles, including doctor, captain, professor, and elder. But the titles I revere most are those of husband, father, and grandfather.
"Dear friends, future happiness and even the future of nations is linked to children. Families with children need to be re-enthroned as the fundamental unit of society. We simply must value children more than we do! Without a new generation to replace the old, there is no wealth; without families, there is no future.
Children come from the union of a man and a woman. The happiest and most secure children come from happy and secure marriages of fathers and mothers. History and contemporary studies have shown that marriage of a husband and a wife, with both contributing their distinctive natural traits to the family, provides the ideal context within which to rear productive, compassionate, and moral individuals.
Any attempt to broaden the definition of marriage to encompass a contractual relationship between adults outside of the traditional family weakens the institution of marriage as God Himself defined it, and undermines the separate, divinely decreed responsibilities of man and woman for procreation, protection, and rearing of children.
Marriage is not simply a contract between individuals; it affects all of society. For that reason, governments have long recognized the family as the fundamental unit of society and have endorsed and encouraged traditional marriage through legal recognitions, protections and benefits.
Individuals and groups who would overthrow the traditional concept of marriage and family would first mutate and then mutilate these long-established, time-tested social norms. The consequences of such changes would have far-reaching implications. If youth were to harbor the belief that the traditional family is but one choice of lifestyle among others, many of them will make choices that will reap only emptiness and despair, both for themselves and for society at large.
Furthermore, those who seek to undermine traditional marriage and family would effectively limit the rights of those who do uphold the sanctity of these institutions. This consequence leads to another major concern— the eventual erosion of religious liberty, including the liberty to defend, promote, and practice traditional family values. Religious liberty is essential if we are to raise up righteous children. Morally responsible families will not marginalize religious liberty, they will nurture and protect it."
I would encourage you to read the full text of the address here. He gives a great overview of the importance of the family and the attacks it is facing in our society.