Functionalists view on sexualityWatch
However, i found this Talcott Parson argument. hope it helps.
"Functionalists such as Talcott Parsons (1955) have long argued that the regulation of sexual activity is an important function of the family. Social norms surrounding family life have, traditionally, encouraged sexual activity within the family unit (marriage) and have discouraged activity outside of it (premarital and extramarital sex). From a functionalist point of view, the purpose of encouraging sexual activity in the confines of marriage is to intensify the bond between spouses and to ensure that procreation occurs within a stable, legally recognized relationship. This structure gives offspring the best possible chance for appropriate socialization and the provision of basic resources."