让你的规则是这样的：

Options +FollowSymLinks -MultiViews
RewriteEngine on
RewriteBase /

RewriteRule ^brands brands.php [NC,L]

RewriteCond %{THE_REQUEST} \s/+facebook\.php\?fb_page_id=([^\s&]+) [NC]
RewriteRule ^ facebook/%1? [R=302,L,NE]

RewriteCond %{THE_REQUEST} \s/+twitter\.php\?twitter_screen_name=([^\s&]+) [NC]
RewriteRule ^ twitter/%1? [R=302,L,NE]

RewriteRule ^facebook/([^/]+)/?$ facebook.php?fb_page_id=$1 [NC,L,QSA]
RewriteRule ^twitter/([^/]+)/?$ twitter.php?twitter_screen_name=$1 [NC,L,QSA]