Random Riddle: What A Character

When I am alone, there is one line for me.

When I have a partner, there are two lines for us.

When there are a few of us, there are several lines for us.

Again, when there are ten of us, there are only two lines for us.

When there are a dozen of us, there are only four lines for us.

When it is our century, our only line is twisted.

Yet when our millenia is upon us, we once again have four lines for us, but not before seeing many more.

We are all the same.

Aside from the first of us, we have a predecessor.

We have been replaced by something that has nothing in it.

What am I?
 

Random Riddle: What A Character