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The marble statue of St Mark on the outside of Or San Michele in Florence was sculpted by Donatello in 1415.
He finished it in 1417.
It was Donatello who was behind that wonderful work. You'll find a link below. The curious person would follow it for more information.
Donatello was not an architect.
He did not co-work with Michelangelo, especially since he died in 1466 and Michelangelo was born in 1475.
Donatello did not have any siblings