Complex sentence: The House of Schleswig-Holstein-Sonderburg-Glücksburg line of succession is based on the Germanic principle of agnatic primogeniture, more specifically an order of seniority among persons and lines of descent from Friedrich Wilhelm, 1st Duke of Schleswig-Holstein-Sonderborg-Glücksburg.
Split into simpler sentences: The House of Schleswig-Holstein-Sonderburg-Glücksburg line of succession is based on the Germanic principle of agnatic primogeniture. More specifically, the status as Head of the House follows an order of seniority among persons and lines of descent from Friedrich Wilhelm, 1st Duke of Schleswig-Holstein-Sonderborg-Glücksburg.