Divide your students into pairs and give student A a blue card and student B a red one.
Students have to ask: Who is Mary? – Answer: Mary is Peter’s wife. Then the student who got the answer writes the name in the blank line. Once the students have all the names, they start asking about the relationship between the family members.
It depends on the student’s level what relationships will be used.
If you want to practice more, you can find more of my worksheets about the same subject here: