Meaning of "head"

“In the UK, most women work outside the home; 21% of families are headed by a single parent (usually female).”

Does this “head” mean that there are parents and children while one parent among the two is the leader of the family, or there is just one parent with children in this family?

Hi

Your second option is correct. The phrase 'families headed by a single parent ’ means ‘single-parent families’. At least in the UK.

Hi apo

Tamara is right. “Families are headed by a single parent” refers to a household with children and only one parent.
There is only one parent living in the house and that parent is therefore the head of the household and/or the head of the family.

Amy