A Diwali Gathering

It was Diwali day. And on this day we decided that my whole family should meet. The gathering consisted of one grandfather, one grand-mother, two fathers, two mothers, four children, three grand children, one brother, two sisters, two sons, two daughters, one father-in-law, one mother-in-law, and one daughter-in-law. We were altogether seven.
How do you explain it?

There were two girls and a boy, their father and mother, and their father's father and mother As it would be too much for words to go into the explanations of relationships here, the most satisfactory thing for you to do would be to sit down, write out a list of the seven people involved, and check off the twenty three relationships.