Dementia family member and selling the house?

Basically there s a dementia family member who doesn t have their name on the deeds of the house but does on the mortgage for the house.

Would this affect the sale of the house?

Additional information: Theres nothing put in place in terms of power of attorney or that for the dementia family member.
Added (1). Edit: Not trying to get PoA, just looking to see if having the dementia members name on the mortgage but not the deed of the house would affect selling.

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