It's just an idea I haven't implemented anywhere yet.
 
Since your members have zodiac sign we can provide them with compatibility texts.
 
Find some free or paid zodiac signs compatibility texts in Internet.
 
(Optional) Create custom page group "Zodiac compatibility texts".
 
Create 12 * 12 custom pages. (Whole lot!)
Labeling them zodiac_Capricorn_Gemini, zodiac_Capricorn_Libra etc.
If your website is multi-lingual better label them zodiac_438_451, zodiac_438_456 etc. Where those numbers are zodiac custom field item ids.
 
After you've created all those pages open your member_profile.tpl for editing and add somewhere link to compatibility page:

What it does. First of all this code checks if profile visitor loggedin, then checks if visitor has zodiac set, then if host member has zodiac set. After successful checks it displays link to custom page depending on two member zodiacs. Remember if you are using multi-language friendly version of custom pages labeling use
{session.profile_zodiac_id} and {profile_field_zodiac_value_id} in your link.
 
Option 1: You can create only one custom page, let's say 'zodiac_compatibility' with all texts inside.
Enclose each compatibility text title in <a href="#" id="Capricorn_Gemini">Capricorn - Gemini</a>
And then if you make link <a href="{virtual_path}page/zodiac_compatibility/#{session.profile_zodiac}_{profile_field_zodiac_value}">{session.profile_zodiac} and {profile_field_zodiac_value} compatibility</a> you'll be leaded to that page and, thanks to anchor, page will be scrolled down to your text.
 
Option 2: You can use any html lightbox solution for displaying compatibility text without need to create custom pages. Create .html pages, according to lightbox solution manuals, upload them to your website document folder and call them from member_profile page.
 
Nothing fancy? Feel free to ask questions if you have any.