Gerhard, Count zur Mark was the de facto ruler of the County of Mark between 1430 and 1461. He was not allowed to use the title Count of Mark in his own rights.

Dietrich was the third son of Count Adolf III of the Marck

Adolf III of the Marck

Adolph III of the Marck was the Bishop of Münster from 1357 until 1363, the Archbishop of Cologne in 1363, the Count of Cleves from 1368 until 1394, and the Count of Mark from 1391 until 1393.Adolph was the second son of Count Adolph II of the Marck...

 and Margaret of Julich.

His father had acquired the County of Cleves in 1368 and given this title to his eldest son Adolf

Adolph I, Duke of Cleves

Adolph I of Cleves was 2nd. Count of Cleves and 4th. Count of Mark.- Life :He was the son of Adolph III, Count of Mark, and Margaret of Julich ....

. The second son Dietrich

Dietrich IX, Count of Mark

Dietrich IX, Count of Mark was the Count of Mark from 1393 until 1398.Dietrich was the second son of Count Adolf III of the Marck and Margaret of Julich....

 received the title of Count of Mark.

When Dietrich fell in battle in 1398, he was succeeded as Count of Mark by his elder brother Adolf. The ambitious Gerhard claimed a part of his father's territories for himself. In 1423, it came to an armed conflict between Adolf and Gerhard, who had allied himself with the Archbishop of Cologne.

Peace was signed between the two brothers in 1430, and confirmed in 1437.
As a result, Gerhard ruled the largest part of Mark, but was to be succeeded by his nephew John

John I, Duke of Cleves

John I, Duke of Cleves, Count of Mark was Duke of Cleves and Count of Mark.- Life :He was the son of Adolph I, Duke of Cleves and Mary of Burgundy...

. He was not allowed to call himself Count of Mark, but has to use the title Count zur Mark.

Gerhard died in 1461 without children and the County of Mark and Duchy of Cleves were reunited again in a personal union under John I.