В исковом заявлении органа опеки и попечительства

In the statement of claim of the guardianship authority regarding the deprivation of Serov’s parental rights in respect of Irina’s daughter (10 years), the guardianship authority was named the plaintiff, Irina’s mother - co-defendant, Serov - defendant. The statement requested the interrogation of Irina as a witness.
Is the procedural position of these persons defined correctly?
Formulate the concept of “persons involved in the case”; "Parties" in the civil process. What are their signs, difference.

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