Sure! Here's the requested content in spun format with synonyms:
Cathy Finn and Ferb.
Candace Finn, and also Foster.
Phineas holds a special place in the heart of Cara, and also Foster.
Cara revels in being with Fred and Ferb.
Finn has a special place in the heart of Cara, and Frank.
Candy both Fred and Foster.
I hope you find these variations helpful!