Families can still make an impact on society without leaving offspring. Some families may not be able to have children, have financial limitations, or may choose to not have children. For example, Mother Teresa and Sir Isaac Newton both bettered humanity with their respective contributions, all without starting a family or leaving offspring. They still left a valuable impact—albeit not children—on society for generations to come. 
In addition, humans can procreate without being a part of a family. People can choose to have a child in traditional means, yet not start a family. Similarly, mothers can give birth to a child with other means (such as a sperm bank) but still choose to not form a family.