As stated above, Alexander I of Russia was the paternal grandson of Catherine II (the Great). He was also godfather to Queen Victoria who was christened Alexandrina Victoria in his honour.
His nephew became Tsar Alexander II, whose second daughter (sixth child) Grand Duchess Maria Alexandrovna married Victoria's second son (fourth child) Alfred, Duke of Edinburgh.
Thank you so much Kempie for your very detailed answer. I'm afraid my knowledge of Russian history is very sketchy. I've now been sent another quiz, so I may have to call on your help again. As it doesn't have to be in for another three months, I'll get this one sent off first. Thank you again!