Franco van Langhel and His Sons with Saint John the Evangelist (outer face); Pieter van Os with Saint Peter (inner face)

For decades art historians asked whether the man kneeling on the inside of this wing could be Peter van Os, and kept answering no. The coat of arms seemed wrong, and so did the saints. In 1998 the Dutch historian G. C. M. van Dijck went back to the town records of 's-Hertogenbosch and argued that it is him after all. The shield beside him joins the ox heads of the van Os family with the arms of his mother's family, and behind him stands his name saint, Peter, holding the key.

Van Os had started as a clerk in the office of the town secretary and married his employer's daughter. In September 1498 he became town secretary himself, and later he wrote a chronicle of the town that runs from Adam to the year 1515. The museum now puts his name in the title.

His employer kneels on the outside of the wing with his sons. Franco van Langel had died a few years before the altarpiece was painted. No saint was called Franco, so the family placed him under Saint John, patron of the town's great church.