We don’t know of any decision that has overridden the Palfrey decision.
If you are living in a multigenerational family with people who do not count as cohabitees or spouses are the owners as tenants in common, I think it is obvious that the share of the person needing care cannot be treated as automatically a pro rata share of the overall value. I think that that would be the case whether or not the persons were joint tenants or tenants in common, and the same whether or not the other owner was living in the house, but your scenario is the strongest scenario and the hardest for a council to get around.
AI says that the co owner in Palfrey was actually a joint tenant. The logic was still that since the co-owner had no intention of buying the share, there was no realistic market for it, leading to a nil valuation.
The valuation must reflect the practical difficulty of selling a fractional interest against a co-owner’s wishes.
However, while Palfrey established that a nil valuation is possible, it is not an automatic outcome. A separate case, Wilkinson v Chief Adjudication Officer, found that a share did have value because the co-owner had merely inherited their interest and did not live there.
I think that you are good to go with it still being the law, as long as you anticipate that there are some councils that will refuse to do a valuation in the hope that you will not get one and then their assumption of the stated percentage shares representing the real value will go unchallenged.
You would want to be saying to the council at that stage that unless or until they have valuation evidence, they can’t levy the charge at all.