In a book by German historian Klaus Bringmann, I read that during the regal period, the whole population was divided into three *tribes*.
He furthermore states that each tribe was divided into 10 *curiae* and *plebs*.
So my first interpretation was that a roman citizen was either part of a *curiae* or he was part of *plebs*. But in either way he belonged to one *tribus*.

However, on the English Wikipedia article about "Curia" it reads that "later every Roman citizen was presumed to belong to one".
Was that something that changed during the republican period or was every citizen part of a *curia* from the beginning?