Combo 2 in 1 website

hi,
i already got 2 website, so other guest must be register in 2 times for login 2 of my website... may i make it oly 1 registertrion to access 2 webite?

example:
www.sioloonfunclub.niceboard.com is the 1st website
www.sioloon.unlimitedboard.com is the 2nd website

if i go to the 1st web... i must register it before going inside the forum or something else. true? ok, for the 2nd web i also want to join it.. so i must register agains.. so this is make other guest confiuse to do it . but they knew the 2 of website make by only one owner/founder and same motivition.

thats all? anyone can help me

note:sorry bad in english

Sorry but for each forum you need to register, and you've got one administration.
You can't combine 2 forums...

But we've got a similar feature on our service http://www.sosblog.com , called "multi-blog"

If you want a multi-forum, please post your idea in the suggestions area

You could make a hyper link to each other? Put it in the navigation?

thanks all .... for the information and suggestion.. peace! any else?