A man nobody can find
People have been looking for the real Robin Hood since at least the 1500s, and they have not found him. There are court records with outlaws called Robinhood in them, but the name turns up so often, in so many places, that historians mostly think it had become a word for "outlaw" rather than a person — the way you might call somebody a Scrooge without meaning a particular man.
What we have instead is older and in some ways better: the ballads. Songs, passed around and sung in alehouses and markets, written down eventually by people who had heard them rather than invented them. The oldest surviving one is from the 1400s. By then the songs were already old.
So the honest answer to "was Robin Hood real" is that we do not know, and that the question may be the wrong shape. He is real in the way a folk song is real.
What the old songs actually say
The Robin Hood of the ballads is not quite the Robin Hood of the films.
He is a yeoman, not a dispossessed nobleman — the aristocratic backstory was added centuries later. He is devout. He is extremely fond of a disguise. He loses fights fairly often, usually to people who then join him, which is more or less how he collects everybody he knows: Little John at a river crossing, a tanner, a potter, a friar who is at least as difficult as he is.
And the famous line about robbing the rich to give to the poor is a summary rather than a quotation. What the ballads show is narrower and more interesting: he takes from people who have taken, and he gives back to the specific person who was taken from. It is less a policy than a habit.
Why it lasted
Six hundred years is a long time for a story to survive without a publisher pushing it, and Robin Hood has done it in every format that has existed since — ballad, play, chapbook, novel, film, and now a great many children's books.
The usual explanation is the obvious one: almost everybody, in almost every century, has known the feeling of being on the wrong end of somebody powerful. A story where that person is outwitted by somebody quicker and poorer does not go out of date.
But there is a second thing, and it is the part we found most worth keeping when we wrote our version. The ballads are funny. Robin is beaten with a staff and knocked into a river and laughs about it. He talks his way out of things. He is generous in a slightly show-off way. He is good company, which is a rarer quality in a hero than you would think, and it is probably why children have liked him for six centuries.
Where Sherwood actually is
There is a real Sherwood Forest, in Nottinghamshire, and you can walk in it. What is left of it is a fragment — a medieval royal forest was not a wood in the modern sense but a legal designation, a stretch of country where forest law applied and the deer belonged to the king.
That legal meaning is the part worth knowing, because it is what makes the story work. Taking a deer to feed your family was poaching, and poaching was punished brutally. The forest in these songs is not scenery. It is the one place the law reached differently, which is why an outlaw could live there and why living there made him an outlaw.
Barnsdale, in Yorkshire, has at least as good a claim as Sherwood in the earliest ballads. Nottingham won largely because the Sheriff did.
Every version is different, and that is not a problem
There is no original Robin Hood to be faithful to. There are ballads that disagree with each other, plays that disagree with the ballads, and five centuries of retellings that disagree with everything.
This is unusually freeing if you are choosing a version for a child. You are not picking between a real one and adaptations. You are picking which of many you want, and the only honest question is which one is good.
It is also why we say what ours leaves out. Our telling keeps the river fight, the archery contest and the Sheriff, and drops the hanging, the prioress and most of the cast — not because those are wrong, but because four characters and one clear grievance is what a five-year-old can hold.
What we kept, and what we changed
The child becomes Robin Hood, rather than meeting him. That is the one real departure, and it is deliberate: a book where your child watches somebody else be brave is a weaker book than one where they are the person deciding.
Everything else stays close. Little John still wins the fight on the bridge. The Sheriff is still certain he is in the right. The money still goes back to the person it was taken from rather than to "the poor" in general, because that is both what the ballads say and the version a child can actually reason about.