coordination - How to parse "one..., the other..." ? Is it a coordinate sentence, which should have a conjunction?

One is Tom, the other is Tom, too.

One lives in a big town, the other lives in a small town.

I think the sentence above are coordinate clauses. They should have a conjunction. They should be:

One is Tom, and the other is Tom, too.

One lives in a big town, and (while) the other lives in a small town.

I wonder which version is right. Why?