A biological father has standing to challenge voluntary declaration of paternity filed by another alleged father. Adrian L. executed a voluntary declaration of paternity upon the birth of the minor and lived with him for the first year of his life. When Adrian and mother left on a trip to Mexico, abandoning the minor, CPS detained the minor and filed a petition. Christopher W. appeared at a hearing and told the court that he suspected he was the biological father. This was confirmed by a paternity test, and Christopher was adjudged to be the minor’s legal father. Upon Adrian and mother’s return from Mexico, Adrian was incarcerated for kidnap of mother. His claim of paternity arising from the voluntary declaration was therefore not heard until later in the proceedings. The juvenile court then set aside Adrian’s voluntary declaration of paternity, reaffirming Christopher’s status as legal and presumed father, and granting him custody. On appeal, Adrian contended that the juvenile court was without jurisdiction to set aside his voluntary declaration because Christopher lacked standing to challenge it. The appellate court disagreed, finding that Christopher’s challenge was authorized by Family Code section 7575. Further, Christopher had a constitutional right under Kelsey S. to contest Adrian’s declaration. Further, Christopher refrained from asserting his rights earlier because Adrian actively and violently coerced him into abandoning them. Adrian is therefore estopped from arguing that Christopher should be barred from asserting Kelsey S. rights.