Jamie's birth story was never truly uncovered. His mum Kim Tate (Claire King) had an affair with Dave, at the same time as planning to get pregnant in order to achieve a greater stake in the Tate estate. Husband Frank, however, was known to have a low sperm count, and so his chances of actually fathering Jamie were low.
Though Kim was in love with Dave, Frank's offer of a million pounds to leave her lover and tell everyone the baby was his ruined any plans she may have had to elope. He also got a DNA test to settle the matter of Jamie's paternity, which revealed him to be the father – however, this is soap world so anything is possible to change. And as if the complexities of Jamie's paternity weren't enough, he also has a thorny relationship with mum Kim.