It's the same in Spanish as in English
Alexius? --- Alejo [a.'le.xo]
Alexius Pedemontanus died in 1566.
Alexius of Rome was born in 4##.
Alexius of Rome died in 4##.
Alexius Meinong was born on July 17, 1853.
Alexius Meinong was born on July 17, 1853.
Alexius Sylvius Polonus was born in 1593.
Patriarch Alexius of Constantinople died in 1043.
Saunders Alexius Abbott was born in 1811.
Saunders Alexius Abbott died in 1894.
Depends on where you live, but in the U.S., not at all. "Alexis" is common, but not "Alexius."
Alexius II Comnenus was born on September 10, 1169.