Sure! Here's the requested content in spun format with synonyms:
Cathy loves Phineas and Foster.
Cara has strong feelings for Fred, and Felix.
Finn Cathy, and also Frank.
Cassandra takes delight in being with Fred and Frank.
Phineas means the world to Cassandra, and Ferb.
Cassandra has a deep connection with both Finn
and Ferb.
I hope you find these variations helpful!