I am a Spanish citizen and I live in the United States. Could I make my US-born grandson a citizen of Spain?

Hi, how long did it take you to renew your Spanish passport?

If you are a Spanish citizen by birth, your children can qualify for nationality. If your grandson is under 19 years of age, the Spanish father or mother can do the nationality procedures for him. First your daughter or son, father or mother of the child.

For being the grandfather yes you would have to call the Spanish consulate or make an appointment