Complex sentence: The Welsh Lord who launched the revellcion against Richard III during the same year that Richard's son died and the Princes went missing, Breckinridge, also had access to the Princes in the tower.
Split into simpler sentences: The Welsh Lord who launched the revellcion against Richard III during the same year that Richard's son died and the Princes went missing was Breckinridge. Brekinridge also had access to the Princes in the tower.