How Family Acheivements Work

For family achievements, both the overall count, and the levels are aggregated from among family members. That means that the count is the sum of the count, and the levels are the sum of the levels of family members. The counts from all family members don't stack to earn family levels. To get a level 1 for the family, a member of the family has to earn level 1 individually. 

Example: if level 1 is 10, and two family members each have 5, neither of them will have level 1. The family will show count of 10 but will not have Level 1. If one of the members then individually gets to 10, they will earn level 1. The family will then show count of 15, and 1x Level 1.