Queen dowager
Sebastian died young and did not marry. However, he was involved in some proposed marriage alliances. In particular, the Queen dowager of France, Catherine de' Medici, nurtured a plan for a long time to marry her youngest daughter, Margaret of Valois, to Sebastian, a plan which was supported by Sebastian's maternal uncle, King Philip II of Spain, on occasion. Later, Margaret married Henry Bourbon, King of Navarre.