Alexader I. He was Catherine II's grandson. He was her choice for next ruler, but she died before she could make that happen so his father, Paul became Tsar. Paul had inherited the soldier play gene, so he eventually got offed and Alexader I came to the throne. He really didn't like being Tsar. He eventually either died or faked his death and went to live elsewhere.
The monarch who started it all, Peter I the Great and I susppect he is with Catherine I.