Anthony van Dyck, the celebrated painter, was born and raised in Antwerp in the beginning of the 17th Century. One would assume, then, that his mother tongue was some version of Dutch.
At the age of 20, he traveled to England, where he was received at the King's court. How did he communicate with the King and courtiers (well enough to get a commission, we're told). What language did he use?
Later, he traveled extensively in Italy, meeting with, and receiving commissions, from Genoese aristocracy. He visited Palermo, where he painted a bunch of pictures.
He returned to England and spent some years there, and was well-compensated there for his work.
He also visited France, where he painted a portrait of Cardinal Richelieu.
Did he speak English? Was he fluent in Italian? What about French? How and where did he learn all those languages?