You can add and delete email addresses here, but of course only your own, not others:
If the invited person's profile still is open for edit because permanent password is not set or he/she have opened up for family to edit their profile you should have a "Add Email" option where you can enter the new address.
The person get a new invite message and you have to ask the person to enter the above link (which you find int the Account /Account Settings menu) and delete the wrong address. There should also be a verify link to test the email.
When entering that setting page you will also be asked to set a permanent password, so make sure that the person set a password he/she will remember because password recovery will not work until the wrong email address is deleted or removed as primary address.
I Invited a relative to join the big tree. He accepted.
He has an unconnected tree he would like to merge with the big tree.
However, he forgot his password and in the meantime his email account has also changed.
What would be the right procedure to recover his password (linked to his old account) or to merge his 2 accounts?
Time to recognize the Help link at the bottom of every page, - under help you also find: http://help.geni.com/categories/10689-Frequently-Asked-Questions