Brand A (site 1)    Brand B (site 2)
---                 ---
site 1 pages        site 2 pages

Brand Unified (site 3)
---
site 3 pages

<VirtualHost *:80>
    ServerName site1.com  #site1.com now points directly here
    ServerAlias site2.com #site2.com points directly but redirects
    ServerAdmin admin@brandAsite.com
    DocumentRoot /var/www/newsite

NameVirtualHost  *:80
<VirtualHost *:80>
    ServerName site1.com
    DocumentRoot /var/www/newsite
</VirtualHost>
<VirtualHost *:80>
    ServerName site2.com

    # Specifically mapped redirects
    Redirect permanent /foo/ http://site1.com/new-foo/

    # Root redirect (if no other cases above match)
    Redirect permanent /  http://site1.com/
</VirtualHost>