Willem van Oranje
The brother who became leader of the Revolt and is regarded as a forefather of the House of Orange-Nassau.
From Nassau to Orange-Nassau
Maria is not a direct ancestor of King Willem-Alexander. She was the sister of Jan VI, ancestor of the Frisian Nassau branch from which the present Dutch royal family descends.

Genealogy
In everyday language, she is a very distant great-aunt. More precisely: she is a sister of Jan VI of Nassau, from whose descendants the line to King Willem-Alexander developed.
Maria’s brother, who became leader of the Revolt and later became known as the Father of the Fatherland.
The brother who became leader of the Revolt and is regarded as a forefather of the House of Orange-Nassau.
The sister who married the Count of Bergh and was caught between brother, husband and war.
The brother whose descendants formed the Frisian Nassau branch and eventually the present royal line.
Maria never wore the Dutch crown, but she stood as an aunt beside the family line that would wear it centuries later.