2 boards sharing same members?

[masterweb]

Hello guys (and gals), i have a question so i need some help:

I'm running an English base board under vBulletin 3.8.2 and i wish to launch a twin of this board but Spanish based running on it's own domain name, it's own vBulletin license and of course it's own database; well my question is:

Is possible o share members between boards ?, my main board is a marketplace so what i want is some similar to Ebay (doesn't matter if a member of Ebay is registered on USA, Asia or Europe with just a click he/she can browse auctions outside and even bid on them without loging in two times). I'm looking for a single access login between these boards so members can switch from board (marketplace) "A" and then continue on board (marketplace) "B" without registerin, logging in two different sites.

Please note that i'm not looking to share threads nor posts from one board to another, what i'm looking for is a system to assign same rights and privileges on both boards with a single account on one of them.

Is that possible?, if yes how can i do that?.

Really thanks for any input or support you may give me.