I think that Willem of Nassau, Prince of Orange was the Pater Patriæ indeed but not the founder of the Orange dynasty in the Netherlands. That honour goes to Engelbrecht I von Nassau-Dillenburg, who married the 11 years old (!) Jehenne de Polanen in 1403, heiress to a dazzling fortune. This marriage would make this German noble family amongst the wealthiest and most powerful nobles in the Low Countries.
1403 Engelbrecht I von Nassau-Dillenburg married Jehenne de Polanen, Lady of Breda
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1442 Johan IV van Nassau-Breda
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1475 Johan V van Nassau-Breda
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1515 Hendrik III van Nassau-Breda married Claude de Chalon, princesse d'Orange
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1530 René van Nassau-Breda, prince d'Orange
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1544 Willem I van Nassau-Dillenburg , prince d'Orange