Which relationship does not satisfy the Relationship Test for a qualifying child for a taxpayer?

Robert for Gwen: Robert (7) is the natural born son of Gwen and Walter.

Gail for Maria: Gail (10), who was born in Tibet, was adopted by Maria when Gail was an infant.

Tim for John: Tim (8) is unrelated to John but lived with him all year, and John treated Tim as his own son.

Tanya for James: James is not Tanya's (17) father but was once married to her mother, Phoebe, when Tanya was age 11 through 15.