I am in the process of editing (or re-writing one could say) the first draft of a novel I have been working on, and I have stumbled across a problem. The story is told using 3rd person omniscient from the POV of three people. One of them is the protagonist and the male lead and from the other two one is the female lead and the other plays an important role up to halfway into the story, from where on she gets significantly less attention. The problem i am having is that at the beginning of the story, the two less significant characters need to appear first for things to be chronologically consistent. If I write it this way, the protagonist will be introduced in the 3rd chapter, and i am afraid it might confuse the readers.
Well, you wouldn't be the first author to do that; plenty of books have prologues (off the top of my head I can only come up with some Tarzan book I read when I was 10 or so, you know, plane crashes into the jungle, the survivors struggle to find food, build shelter etc. then some catastrophe befalls them and lo and behold, the hero enters the story). Just make the beginning interesting and captivating and imo you shouldn't have any problems if you introduce the main dude in the next chapter (unless his first appearance is 100 000 words into the story).
I don't think it's too much of a problem as long as the beginning chapters are interesting. Look at the formula for a lot of slasher flicks. They usually start off with a killing of some kind. The victim is almost insignificant or irrelevant, but is still important because it sets up the threat of the story, provides suspense and to some extent sets up the story the protagonist will find themselves in. I'm not sure if that specific formula can be used as a guideline for the genre you're writing in, though.
I was facing a similar issue. I've been working on a story for years. It started as a short story that I wrote in 7th grade (based on a character I imagined in Sixth grade), then a sequel some time later. But the sequel was too big and needed a third part to continue... by the time I started the third part I was in at least my sophomore year because I was given the very crucial idea to turn it all into one book and was busy reworking a couple hundred pages while writing the new material. I advise against trying to turn sequels into one coherent book unless it all fits better as one story. Long story short, Image (my story) had changed so much in story, focus, depth, and characters, and my writing style had grown and changed so much, that when I was a senior in high school I faced too many challenges to continue, despite having a nearly complete, 300 page work. Why does that matter? Well now that I've restarted--from the beginning, mind you-- I face the dilemma of what story I want to tell. What characters are really important? Who is the main character. Because the Second part was written as a sequel, the first main character lost a lot of importance and even died. He would remain insignificant for most of the story after that, leaving his Apprentice as the new MC. But that precludes all need for the first part. No problem, right? Just omit it. Here's the catch. The second part following the apprentice takes place in a universe that was created entirely by the first MC... the challenges they face are direct results of events that happen in the first MC's life because the villain is his alter ego personified--pure evil with god-like power. To further convolute things the First MC plays an important role as a mysterious phantom character after he "dies". So with the Two MC's playing very intricate roles in the story--the first MC unable to beat himself relies on his apprentice/son to do it-- My job is to decide what the story is and then determine which characters drive the story. I also have other characters who have importance in the beginning, but do next to nothing for a while. What I have to do is either give them more importance in the later part of the story, for balance, or remove their role entirely. Cutting hurts, but I've removed large sections already even whole characters and story arcs. Pardon my long-winded reply, but I see nothing wrong with your main protagonist coming in later, but he would then have to introduce a large enough shift to make the readers care about him. Perhaps shorten the earlier portions or find a way to introduce him sooner? If not, find a way to make the first characters important later on. If you can't find a good reason for readers to get less time with them, why they contribute less.
I am, or will after my rough draft is done anyways, dealing with the same issue more or less. I have about 5 povs, and to keep things linear ill have to start it with someone else. The only difference is that I do have a prologue. It's not in the pov of the protagonist, but it introduces him and (hopefully) makes the reader care what happens to him. The prologue happens about 2 years prior to the beginning of the book. But to answer your question, I don't think it matters that much. Like others have said as long as you can trap your readers attention you can start with whoever you need to. But in the end you could add in a prologue that deals with the protagonist if you'd feel better about it.