What’s the change in American family in the 21 century?

At the beginning of the twentieth century, many people thought that the American family was falling apart--in other words, they thought it was dying. A century later, we know that this was not the case. However. although the family is still alive in the United States, its size and shape are very different from 100 years ago.
   In the late 1800s and early 1900s there were mainly two types of families in the United States: the extended and the nuclear. The extended family usually includes grandparents, parents, and children living under the same roof. The nuclear family consists of only parents and children. As people began to move to other parts of the country to find better jobs, the nuclear family became the most common family structure, or unit.
   Today there are many different kinds of families. Some people live in "traditional" families, that is, a stay home mother, a working father, and their own biological children. Others tire in two-paycheck families (where both parents work outside the home), single-parent families (a mother or father living with the children), adoptive or foster families (where adults take care of children that are not biologically theirs), blended families (where men and women who were married before marry again and combine the children from previous marriages into new families), childless families, and so on.