Mon Mothma is easy to explain.
The one that is/would be hard to explain is Biggs.
If that is Biggs then we do actually have a continuity problem on our hands. When Luke runs into him at Tosche Station he states his intentions of jumping ship and trying to join the Rebellion. He doesn’t supposedly join the Rebellion until sometime after that before Luke makes it to the Hidden Base.
Now, some will say that it’s a deleted scene and therefore doesn’t count. HOWEVER, it’s been officially stated that the novelizations of the films are canon and that scene is included in the novelization of Star Wars.
Theories?
I’ll never understand why they ever said that the novels are canon )unless its a misunderstanding and they meant the new-EU novels and NOT the movie adaptations). If they are then Owen is Obi-Wan’s brother and Padme married Bail Organa.