Athletic Club forward Nico Williams says it was a natural choice for him to play for Spain, while his brother chose Ghana.
The two brothers, born in Spain to Ghanaian parents, made their international debuts for their respective countries last week.
Inaki appeared for Ghana in the second half of their international friendly loss to Brazil on Friday.
The next day, Nico played for Spain in their shocking Nations League loss to Switzerland.
After making one cap for Spain, Inaki switched to Ghana earlier this year.
Inaki's decision increased Ghana's chances of also securing Nico, but Spain acted quickly and capped the youngster.
"It was a natural decision, each one took their path and made their decision in a thoughtful way.
"I am very happy that my brother is in Ghana, I wish him things to go well, that he can have a great World Cup and achieve the highest goals," Nico said.
Inaki and Nico are hoping to make the Ghana and Spain squads for the 2022 World Cup in Qatar.