This document, found in the Buffalo Library, states that John Holly came to America on the Mayflower in 1625 with three brothers.  This supports the hypothesis that Samuel and Elizabeth Holly, who came in 1635, might be John's parents, and came five years later.

This document, also found in the Buffalo Library, has John Holly coming to America in 1630.  This is consistent with the history of the Mayflower. It's third trip to America was in 1630 with the Winthrop fleet..