I understand that you can withdraw up to $10,000 out of your Roth IRA to be used as the downpayment of your first home after we have opened the account for five years to be exempt from the penalty. Can both my husband and I do this and have $20,000 to use towards the downpayment or only one of us can?

And do we have to eventually pay this $10,000 back into the Roth IRA account?

Thanks!

Well, your message is obviously the most unusual this board has seen. Congratulations on your wedding.
You can withdraw contributions you made to a Roth any time, tax and penalty free.
What you may be reffering to is a Qualified distribution which means you and your husband are EACH eligible to withdraw up to $10,000 in Earnings, after the Roth is open 5 years for the purchase of a home under the 1st time home buyer exception.
So if you each had contributed $15,000 from 2001-2005 and were fortunate enough to see that grow to $25000, then ALL of the $25,000 could be withdrawn and you would owe no taxes on the $50,000 between you.