Sweet Tooth and Kratos were created by David Jaffe. But at this point I don't wouldn't really know the reasons. We've been getting a lot of hints that R&C and J&D will be rivals rather than J&D vs Nathan Drake.
Due to both been from Sucker Punch I'd say Evil Cole and Good Cole will be rivals.
Going by what we know so far:
Nariko and Dante - Both Ninja Theory Sweet Tooth and Kratos - Both from David Jaffe. Heihachi and Toro - Both Japanese? Big Daddy and Sackboy - Random
Unconfirmed Jak & Daxter and Ratchet & Clank - Random Spike and Parappa - From the Voice acting things.
My guess after that would be:
Fat Princess and Sly Cooper - Sly steals some cake fat princess looking for. Raiden and Radac - Radac is looking for a cyborg to help him in the war and wants to use Radien. Sir Daniel and Nathan Drake - Drake is looking for relics/treasure and finds Sir Dan.
One who knows nothing can understand nothing - GamerTag: wwinterj/PSN wwinterj