The bond between brothers and sisters is the longest-lasting bond that an individual nurtures throughout his life. In a brother or sister, the child finds an ally, a protector and a model, with the help of who he prepares to function in the world outside the family. The potential for mutual developmental influence is unquestionable and additionally emphasized when it comes to the presence of a developmental disability of one of the members. Speaking of the field of hearing impairment, interest in hearing siblings as research subjects is still rare. Thus, the goal of this paper is to gain insight into the experiences of adult hearing brothers and sisters of people with hearing loss in terms of growing up, communication, family and social relationships, and professional support. 8 hearing adults, whose brother or sister is a deaf person within a hearing family, participated in the research. Data were collected through a semi-structured interview, followed by a qualitative analysis based on the principles of the grounded theory method. The results show that the influence of hearing siblings is strong enough to contribute to the progress of a deaf child. In order to use this influence, they need a language, which was not offered to them in a timely manner, what they attribute to the professional support system. Sign language would thus enable the earlier development of a close relationship, which would consequently contribute to better therapeutic outcomes. Hearing brothers and sisters contribute to the quality of life of deaf people and take on the roles of translators and advocates for them in the hearing world, at the same time immersing themselves in the world of the Deaf, which they consider irreplaceable for their brother/sister. For deaf brothers and sisters, they are lifelong allies and support, whose role in the process of providing professional support justifiably deserves its place.