The marriage index for their son Romano Dominguez states that Romano was from Guerrero, Mexico and his wife was from Laredo. So I am assuming that this is Guerrero, Tamaulipas which is near Laredo. Also, FamilySearch does provide another couple with similar names to Victoriano and Germana and they are from Zacatecas and Aguascalientes. Sorry, I could not find more.