Your father's old hearing aids will not be the best for your mother. First, if your father's hearing aids are '' old '' they might not be working up to technical specifications. Since hearing aid technology has changed dramatically in the last years, the technology used in your father's hearing aids could be obsolete by now. Secondly, your mother has a particular hearing loss different from your father's. She has specific needs that must be addressed with new technologies that is available. Thirdly, hearing aids are custom made. No two ears are the same and, therefore, your father's hearing aids will not fit your mother's ears. You should have your mothers hearing tested thoroughly by an Audiologist, who will be able to recommend the most suitable hearing aids to match her hearing needs.