Complex sentence: It is split into two branches; the elder is known as the House of Welf-Este or House of Welf (Guelf or Guelph), and the younger, known as the House of Fulc-Este or later simply as the House of Este.
Split into simpler sentences: It is split into two branches; the elder is known as the House of Welf-Este or House of Welf historically rendered in English, Guelf or Guelph. The younger, as the House of Fulc-Este or later simply as the House of Este.