Was Benjen stark a White Walker?

You guessed it, Benjen is a White Walker…

That’s why he was able to maintain loyalty to his family and help Bran and Meera.

What did Benjen Stark become?

9 Why Didn’t He Become A White Walker? Benjen also explains that he would have been turned into a Walker, but the magic was stopped by the Children of the Forest and their own magic. They shoved a dragonglass dagger into his chest which stopped his transformation.