The family party

Puzzle Question:

There is a family party consisting of two fathers, two mothers, two sons, one father-in-law, one mother-in-law, one daughter-in-law, one grandfather, one grandmother and one grandson.
What is the minimum number of persons required so that this is possible?

Answer --

Solution of Puzzle:

There are total 2 couples and a son. Grandfather and Grand mother, their son and his wife and again their son. So total 5 people.
Grandfather, Grandmother
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Son, wife
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Son

Toughness:

Intermediate