Count distinct individuals:
- 2 grandparents pairs = 4 people.
- 1 single grandfather + 3 grandchildren (2 grandsons, 1 son) = 4 more, but sons can be fathers already counted.
- 1 single grandmother + 3 grandchildren (2 granddaughters, 1 daughter) = 4 more, but daughters may be mothers already counted.
By optimising overlaps, total = 14.