Divorce was generally rare historically (although this depends by culture and era), and divorce especially became very difficult to obtain after the fall of the Roman Empire, in Medieval Europe, due to strong involvement of ecclesiastical courts in family life (though annulment and other forms of separation were more common).
In the United States, since the 1960s, there has been a marked increase in the number of children living with a single parent.
Sometimes, one finds themselves in a single-parent family structure that has arisen due to death of the partner, intentional artificial insemination, or unplanned pregnancy.
Historically, the death of a partner was a major cause of single parenting.
The 1980 United States Census reported that 19.5% were single parent households.
The ONS reports that those children are twice more like to suffer from mental illness.There are even some that argue that a single parent family is not even really a family.