Is it permissible for a father to take back his ex-wife, who is suffering from cancer and is unconscious, into his responsibility to treat her using his insurance, even if one of the children is not pleased with that?

If the divorce is revocable and the iddah (waiting period) has not expired, the husband has the right to take back his wife without her knowledge or consent, based on the Almighty's saying: "And their husbands have a greater right to take them back." This is because taking her back is a retention of the wife by virtue of the marital bond. However, if the wife becomes irrevocably separated due to the expiry of her iddah or because the divorce was irrevocable, she is not permissible for him except through a new contract, the validity of which requires her consent.