does this need a comma:

Over six billion souls in the world and they all have something in common.

Thanks for ur help.

2 answers

No, but it needs a verb in the first half of the compound sentence.
Yes, after "world", but it's not really grammatically correct even then. There is an implied but missing "There are.." at the beginning of the sentence. As another option, you could omit the words "and they all" and not have to use a comma.