When the family therapy pioneers were writing in the 1960s and 1970s, single-parent families were not nearly as common as they are today. Hence their emphasis was on the more traditional nuclear families. However, as single-parent families make up a significant fraction of today’s families, we need to consider how to adapt the family systems concepts to these families. In single-parent families, there is often a loosening of generational boundaries between the single parent and an older child, who may be recruited to serve as a parental helper. This is adaptive as long as the parent remains solidly in control and the older child remains in the role of the child and is not recast into a co-parent. Likewise, the child should not be cast in the role of substitute spouse, responsible to meet the emotional needs of the parent.

There is also likely to be more involvement of extended family members with single-parent families. This can be an extremely important source of support for the family, but also raises issues about the boundaries of control, involvement, and decision-making power between the parent and the grandparents, aunts, uncles, etc., who contribute to the upbringing of the children. For example, how much does a young single mother make her own decisions about her children and how much does she bow to the advice of her mother?