"Neither... nor..." and "either... or..." [duplicate]

I have some issues with this sentence:

I don't know Alex and Marla.

Is it correct to write it like this:

I don't know either Alex or(or it's "nor"?) Marla.

Or like this:

I don't know neither Alex nor Marla.

And another thing:

May I say something like

I don't know Alex nor Marla.

or

I don't know Alex or Marla.

I don't know Alex and Marla.

You can negate your "knowing" in at least three ways:

• I don't know Alex and Marla. [Used, for example, when Alex and Marla are a couple--married or otherwise, and they are kind of lumped together.]

• I know neither Alex nor Marla. [In English, we avoid the "double negative," so "I don't know neither Alex nor Marla" is not correct. In Spanish, double negatives can be quite correct.]

• I don't know either Alex or Marla.

There are, of course, virtually endless possibilities if you play around with the basic syntax of the above sentences (e.g., "Alex and Marla? Nope, don't know 'em"), but those are the basic three.

As for

"I don't know Alex nor Marla" and "I don't know Alex or Marla,"

The latter is correct. Moreover, it avoids the "double negative" of "don't know" and "nor" in the former sentence.