Possible Clues:

• Czar named "The Great"
• Czar named 'The Great'
• Leader called 'the Great'
• Founder of the first Russian naval base
• Half brother of Ivan V
• Russian modernizing czar called 'The Great'
• ''Great'' Russian reformer
• He ruled jointly with Ivan V for nearly 14 years
• Czar called "the Great"
• Revered Russian reformer