Part I and II of the Gotha is formed by reigning, former reigning and mediatized Houses.
But before the Nassaus became a sovereign House (Princes of Orange) in 1530, they were a par with other families in the Netherlands as De Lannoy, Arenberg, Egmont, Croÿ, Ligne, Berlaymont, Montmorency, Lalaing, etc. Of course history was kind to the Nassaus, resulting in today's the Netherlands and Luxembourg but in anciennity and prestige De Lannoys also have old papers.
That the House De Lannoy is ancient and had the highest standing already becomes clear when we see that no more three brothers (!) De Lannoy are amongst the first Knights of the Golden Fleece in the year of its foundation (1430):
1430 Hughues de Lannoy, Seigneur de Santes (1384-1456)
1430 Guilbert de Lannoy, Seigneur de Villerval (1386-1462)
1430 Baudouin de Lannoy, Seigneur de Molembaix (1388-1474)
Other De Lannoys: 1451 Jean de Lannoy, Seigneur de Lannoy (1410-1493)
1481 Baudouin de Lannoy, Seigneur de Molembaix (1436-1501)
1491 Pierre de Lannoy, Seigneur de Fresnoy (1445-1510)
1515 Charles de Lannoy, Seigneur de Senzeille (1482-1527)
1531 Philippe de Lannoy, Vicomte de Sebourg (1460-1535)
1531 Philippe de Lannoy, Seigneur de Molembaix (1487-1543)
1546 Philippe de Lannoy, Prince de Sulmone (1514-1553)
1546 Jean de Lannoy, Seigneur de Molembaix (1509-1560)
1559 Baudouin de Lannoy, Seigneur de Molembaix et de Slore (1518-1559)
1559 Charles de Lannoy, Prince de Sulmone (1537-1568)
1585 Horace de Lannoy, Prince de Sulmone (died 1597)
1638 Claude de Lannoy, Comte de la Motterie (1578-1643)
1744 Eugène de Lannoy, Comte de Lannoy, 1686-1755)