Is there any rule regarding at which stage of the novel the main character make his first apearence ?
Rules is a firm word. Unless it's grammar, I'd say rules and writing don't always go hand in hand. You would need a pretty good reason not to include them in the beginning, though. Without a main character to care about your readers might not find a reason to stick a round. Why do you want to introduce your character later, and when in the book would you introduce them?
If there's a part of your story that you need to have to explain later plot points but doesn't have any of your main characters, then that's usually what you'd call a prologue. Regardless, your main characters, both protagonists and antagonists, should all be either introduced or referenced within the first act. If you have any Deus Ex characters, then you should probably bring them up here, too, to make them feel less Deus Ex-ey.
I agree with The Dapper Hooligan. You could write about a time before the character is born, but it would probably be a prologue or such. Just don't wait too long to actually get to the main character, and with them the actual plot.
Yes i do need this chapter which will bring my main character into life who latter at his adulhood age will be in collision course with his dad . They do ignore each other their family relationship because the son is a sexual assaut fruit . I home you understand partially the plot. Think you for your contribution.
Every character comes into life, in the sense of being born. Not every character has a chapter devoted to his or her birth.
I think it's a prologue rather than chapter one in the first Harry Potter book, but - the main character is alive but a baby and more of a macguffin than a character. The concept of his existence is introduced, though. That seems like it might be a bit similar to what you're describing? I'd point out that it's a pretty short introductory 'chapter' in HP. You don't want that kind of thing to drag on.
I always regarded that chapter as a waste of space. A harmless waste of space, but a waste all the time. Edited to add: Which is not in any way intended to disagree with your point.
Thinking about it critically, I guess it was probably meant to be a hook for the magical stuff, since there was a bit more mundane story before Harry got to the wizardy content, and with it being for kids that works since you don't want'em to get bored or whatever. But yeah, it probably could've been streamlined a bit more, especially for an adult audience. If I were writing something like it, I'd take a more 'just get to the point faster' approach, but I know that - reading it for the first time as a kid - that opening scene always stuck with me as cool and whimsical and magical and all that. Now I'm just talking about Harry Potter for no reason, though. Digressions aside, @Everlast, what I mean is that you can take some time before you introduce your mc, sure. But it should probably be about them in some way (it sounds like in your case, it is), and it should probably be brief. Personally, I'd give it a pretty hard look and be %100 sure that it's really the best or only way to start things off. I'm not on the completely anti-prologue side of things, but I do think you need a good justification for starting the story at any place other than when things truly get going. (Granted I've also cut my teeth primarily writing short stories, not novels, where getting right into things is kind of a necessity, so.)
Not sure that devoting a chapter to this would be the best way to approach it. Since the son isn't born with the knowledge that he is the result of a sexual assault (perhaps "rape" would be more accurate), I would think the better course would be to have the reader discover this fact at the same time the son does, so as to share his emotional reaction. By showing the rape (which I presume is Chapter One), you attach the emotional response to the mother, not the son.
