well technically the requirements are to be a “natural-born citizen” of the united states, be at least 35 years old, and have been a permanent resident for at least 14 years in the US. then the definition of “natural born citizen” is defined as someone who has been granted citizenship at birth. which he would qualify under. It doesn’t indicate anywhere that both parents have to be citizens for it to apply if he is born in another country. Since he had 1 parent who was a US citizen at birth he was granted citizenship at birth, which would qualify him.