John IV then joined the opposing side, which was led by Margaret's son William V. He supported his half-brother with a loan when he later had a conflict with the Oversticht area.

He created an alliance with Gerard III van Heemskerk, Ghisbert II of Nijenrode and John I of Egmond against Margaret's supporters.

He fought in the Battle of Zwartewaal in 1351 and led the Cod troops during the Siege of Geertruidenberg.

In 1355 William V made peace with the Hook faction and forced John IV to give up some of his land.

John IV opposed Albert, preferring that William's wife, Matilda, should become regent.