The Role of Family and Individual Factors in Going Through Adolescence - Perspective of a Healthy Child.

The goal of this observational study is to investigate the specificity of the growing up process in young people with disabled siblings. The functioning of adolescents with disabled siblings as a person growing up in three environments will be examined: family, peers and school. The main questions it aims to answer are: * Does having a disabled sibling influence the functioning of a healthy child in the family system? * Do siblings of disabled children show a higher level of maturity than their peers with properly developing siblings? * Does having a disabled sibling modify a child's functioning among peers? * Does having a disabled sibling modify healthy adolescent's educational experience? * Is there a greater risk of psychological disorders among siblings of disabled children than among siblings of normally developing children? The 160 participants' dyads will take part in the study: healthy adolescent having disabled sibling and one of his/her parents. The parents' participation is necessary to assess the presence of possible internalizing and externalizing disorders among adolescents taking part in the study. The healthy adolescent will be filling out questionnaires regarding the remaining studied variables: functioning in the family - siblings relations, parental attitudes; at school - school achievement, extracurricular activities; relations with peers - time spending with peers, number of friends, as well as the growing up process trajectory - parentification and the way of going through an adolescent crisis. Researchers will compare four groups (40 dyads in each group): three groups of adolescents having disabled sibling 1) intellectual disability, 2) motor disability, 3) chronic somatic disease, and 4) control group - healthy adolescent having sibling without any disability, to see if they differ from each other referring to the studied variables.