you can't play the same game at same time unless each person has their own copy of the respective game

So if owned a copy and my daughter owned a copy. We all family share could they 2 not play together as one would be using my copy. Is that not the case?

引用自 tezman1a：

If I have myself my daughter and my son family sharing. Say me and my Daughter both own a copy of a particular game i am aware we can both play. Question is if the game is owned by myself and my daughter can my son play if my daughter is not on. So say me and my son play would it make me use my copy and him use her copy?

If there is copy of a game free (as in not being played) in your Steam family, anyone in your steam family can loan it and play it so if you have 2 copies of game owned in the family any two people in your family can play them at a time. Do note that what DLC you get to play depend on the copy you're playing (ie say you own full game with all DLC and there's another copy with no DLC, someone borrows your copy then you can only play the game without DLC until the game with DLC is free again)

There are limitations to the system:
Free games and DLC can't be shared, at all.
Games that require 3rd party accounts or launchers can be shared (EA, Rockstar, Ubisoft etc)
Games that do not support family share can't be shared (developers can opt in or out any time they want).

引用自 tezman1a：

So if owned a copy and my daughter owned a copy. We all family share could they 2 not play together as one would be using my copy. Is that not the case?

Yes, they could play together assuming no limitations apply (see above) and as long as 2 copies are owned and available (not being played at the time). For all 3 of you to play together you'll need all accounts own their own copy.

Oh and Steam Families has it's own forums:

https://psteamcommunity.yuanyoumao.com/groups/steamfamilies/discussions/