Re: Aliens with one name vs. aliens with two names
such as "Worf, Son of Mogh." (Although since he was adopted, his full legal name should be Worf Rozhenko.)
Adopted children don't alway take the family name of their adopted parents, or keep it in adulthood. One of my cousins, who was adopted into the family at age nine, asked to be able to keep the last name of Sanchez out of respect for her late father. It's her legal name.
TOS, TNG and VGR never mentioned a "Federation President."