The person I have in mind is Barack Obama, who was born in Hawaii in 1961, two years after it became the 50th state in 1959.
Suppose he had been born in 1957 (my birth year) that is, before Hawaii became a state. Would Hawaii's subsequent statehood retroactively have made him eligible to run for, and be elected President even though that would not have been case when he was born?
Edit: In answer to the comments, the issue is not whether the parents were native born or naturalized, or even citizens. The issue is, if you were born on soil that "subsequently" became a U.S. state, does that retroactively make you a "native born citizen" like you would have been if you had been after statehood.