Similar to older family sharing with stricter restrictions on adding and removing people(1yr cooldown)
Only upside is both can play simultaneously if playing different games.
They will not reveal the true check but the intention is that it is really a family using it.
While we know that families come in many shapes and sizes, Steam Families is intended for a household of up to 6 close family members.
To that end, as we monitor the usage of this feature, we may adjust the requirements for participating in a Steam Family or the number of members over time to keep usage in line with this intent.