Gerard III fathers Sir Wouter van Heemskerk, who dies without legal offspring.

She had first married Jan Mulaert, a relative of the Van Borselen family from Veere and Sandenburg Castle.

[10][11] Craandijk states that Beatrix married Gerard II, widower of Ada, and got Willem van Haerlem[12] and Hendrik.

[13][14] Muller stated that Beatrix married Gerard III, and got Wouter and Hendrik.

The idea behind the marriage was probably that Oud Haerlem would remain in the family via the female line, i.e. would come to the children of Jutte or Beatrix.

Like dozens of other fiefs, the Count of Holland first held Oud Haerlem for himself, and then granted it to one of the members of the Polanen / Duvenvoorde clan.

[17][18] In January 1300 Gerard III's father Gerard II van Heemskerk had transferred his allodial Heemskerk Castle (currently known as Marquette Castle) to John II, Count of Holland, and had it granted back to him as a fief inheritable by sons, daughters and even sideways.

[11] In 1254 an Arnoud van Heemskerk was bailiff of Kennemerland and burgrave of Torenburg, a castle near Alkmaar.

In late 1351 Gerard was part of the diplomatic mission to get the hand of Maud of Lancaster for Count William V of Holland.