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