What is the ruling on a brother squandering a trust and refusing to return it to his sister?

If the deposit is lost due to negligence or transgression on the part of the trustee, he is obliged to guarantee it. However, if it perishes without transgression or negligence, he is not liable for it. This is the opinion of the majority of scholars. Some of them held that if the deposit is lost from among the trustee's own property, he is liable for it. However, the first opinion is more correct, because the deposit is a trust. It is necessary to refer to the Sharia judiciary to rule on such cases.