All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad (sallallaahu 'alayhi wa sallam) is His slave and Messenger.
It is not permissible for a person to take any of the wealth of his family members without their knowledge and approval. Simply alleging that they were responsible for his illness and therefore obligated to bear the cost of his treatment, does not justify taking their wealth without consent.
Ibn ʿAbbās
reported that the Messenger of Allah (sallallaahu 'alayhi wa sallam) said: “If people were granted everything they claimed, some would claim the lives and wealth of others. Rather, the oath is required from the one against whom the claim is made.” [Al-Bukhārī and Muslim]
As-Sanʿānī
explained in Subul as-Salām that this ḥadīth establishes an important principle: a mere claim is not accepted on its own. Instead, it must be supported either by valid evidence or by an oath taken by the one being accused.
We ask Allah to grant him healing and complete well-being.
Allah knows best.