(in English) Thesis deals with biological children of parents, who have other kids in foster care. These kids are often neglected. In the theoretical part are described and defined terms such as a substitute foster family and its forms, family, siblings. It focuses also on selected foreing researches and contemporary Czech works on this topic. Practical part contains analyzes of interviews with respondents. The main aim was to find out what biological children of their parents in general think of foster care. How they perceive the situation in their own family and how it affects them.