Davo's Released Mods, and Some Unreleased. These are made for Galactic Adventures with patch 1.5.1, but some of them may still work on Core Spore. No harm can come from trying, as long as you've made a backup.
Is there a mod which adds more pack members mod?
i think creature Overhaul?
I have Creature Overhaul, it does not add more members to your pack.