Along with conventional notions about the positive influence pets on the development and psychological well-being of children, an increasing number of investigations evaluate the role of pets in the life of the modern urban family more carefully. Existing contradictions can be resolved via submission on pets as integral and important parts of the entire family system: the emergence of pets in the family may be associated with the maintenance and regulation of its homeostasis. We tested this assumption in the empirical research, which objectives were: 1) identification of the association between the age of the child/ siblings and appearance pets in families; 2) correlation of the data with the stages of family life cycle. Based on the data obtained from the survey (n=658) among students, conducted among first-year students of the faculty of psychology of Moscow State University and among the clients of the veterinary surgeon in 2008—2012 (n=75), we have analyzed the dependence of the frequency of occurrence of pets, which respondents considered “family member”, on the age of child/children in the family at the time of their purchase. According our findings pets’ appearance in a family with the only child happen when the child is 7, 9, 13, 16 years old, in a family with two children it happens when the second child is 7, 9, 13 years old and (or) the first one is 12—16 years old). These peaks happen when families have normal crises, not related with the changing family structure, but with the other factors, particularly with necessity contacting with social surrounding or with strict changing demands of psychical development of the child. The peaks of appearance pets in a family which were found by us can be evidence of including pets in regulation homeostasis of family life.