If my sister is on the deed by joint tenancy do we still have a case to fight on my moms side since she has passed awayand my sister new that my mom wanted the house for all her kids

Joint tenancy in common or joint tenancy with right of survivalship

In Joint tenancy in common then when one of the parties that own the property dies, their heirs inherit the property and are then part or co owners of the proper in common with the other owner.

If the joint tenancy was with right of survialship then when the one person dies, the other or others take over that part of the ownership.

If your mother wanted all of you to own property together she should have added all of your names.

So as I mentioned before, you need to have someone pull the deed and see exactly how it is written.