Answer:
De padres argentinos, Julio Cortázar nace en Bruselas en 1914.
Explanation:
This means: Of Argentinian parents, Julio Cortázar is born in Brussels in 1914.
"Junto a" is a correct expression but is semantically incorrect, because it would mean Julio is born along with his parents. The verb "nacer" is always followed by "en" when referring to the location of a birth. The correct preposition when talking about dates and years is "en".
