Complex sentence: Richard III had asserted that her father Clarence's attainder barred his children from any claim to the throne and her marriage arranged by Henry VII to Sir Richard Pole was not auspicious but it did allow the couple to be closely involved in court affairs.
Split into simpler sentences: Richard III had asserted that her father Clarence's attainder barred his children from any claim to the throne and her marriage arranged by Henry VII to Sir Richard Pole was not auspicious. However, it did allow the couple to be closely involved in court affairs.