To be friend .
Not exactly "same time" but close. When Kushina was pregnant Sasuke was already born.
They wanted them to grow up together and become great friends and strong shinobi (Sasuke is named after Hiruzen Sarutobi's father, Sasuke Sarutobi in hoeps that he would become just as splendid a ninja) and Naruto's parent's help high expectations for their son (particularly Minato when he stated he was sure Naruto would be the one to stop Tobi).![]()
never knew which was born first.