Siblings of people with disabilities face a variety of problems, including problematic behavior of classmates, bullying and teasing because of their sibling’s disabilities, and concern for their parents. The purpose of this study was to examine the experiences and feelings of siblings of people with disabilities and to consider how to support them according to their developmental stages. A one-hour semi-structured interview was conducted with one adult who had a sibling with intellectual disabilities, asking about (1) the experience of being involved with the sibling and thoughts at that time, (2) the way others interacted with the sibling and thoughts about it, and (3) what kind of support was provided. The data from several previous studies were used to capture the characteristics of each developmental stage. We found that in the early childhood period, when children noticed the disability and asked questions, the correct knowledge was conveyed to them in a language that they could understand. In the school-age period, when adults around them made sympathetic remarks, the adults close to them summarized the remarks and conveyed their true intentions. In the junior high school period, when they were taking care of their siblings, the adults spoke to them in a way that did not burden them. In junior high school, it was necessary to convey a message that did not burden those taking care of their siblings. In senior high school, it was necessary to take concrete measures such as verbally telling siblings that you are looking out for them as well as your own siblings when it may cause conflicts between siblings.