On the nature of secondary character:
After having posted the reply above, I have though for some time (not much) about what makes a secondary character and not.
We have estabilished that people with split personality, and people that exchange place with another, are to be considered a single character. That's obvious, I think, altough it force us to know and understand two or more different people. But they are not present at the same time, so that would never broke the rule #1.
Other cases.
Tobias Christopher, at the beginning, was written, by his poster, as being ALWAYS followed by the cat Lil' Jo. If TC would be in the lost in space story, and written right, would the cat be allowed to come? I guess so, being it something that doesn't talk or even think, a mere presence, like a walking piece of equipment.
Chance
Chance, altough the thing was used very sparingly by TTT, had the ghost of Pete as a companion (or a nuisance), following him closely. He talked, though, and was able to make decisions, altough it was bonded to the Swedish chemist. Would he be allowed in the story or not?
Sir Justin (from the old Universe)
Sir Justin, a TTT character form the original MBL, was a medieval warrior from a fairy land, that traveled the country riding a talking hawk-pigeon.
Would that animal be considered a secondary character and not be allowed in the story, if Sir Justin would be the actual TTT hero? It talks, it is able to do things on his own. But, I guess, not allowing it in the story, it would "alter" the nature of the character.
My question is: how the rule #1 can condition the kind of character we can create?
A guy with his own pet giant robot, is one character, two characters, or one main and one secondary character? And what is the main, and what the secondary one?
A man and a woman that mistically merge to create an androgynous uber-mage, what are? Two characters or just one? Or three? How mains, and how secondaries?
Secondary characters, for me, are people that are totally separated and can stand a full separate life from the main character to which they are relate. Quantos is a secondary character. Miss X is. Charley is. Kit is.
But Eddie could be really considered a secondary character? Do you really think he could be exist separated from Euro?
Why Drake talking mentally to Drax, or Danny and Hal, should be less problematic for that story than Euro talking to his son, KNOWING that the kid would not talk back?
And even if he would not come, do you think that Euro wouldn't think to him constantly? Or Phil not thinking about Leslie? The presence of Eddie wouldn't be felt less if he was phisically present, of that I am sure.