to answer your question in regards to Silver the Hedgehog (Pre-Super Genesis Wave) Sega is a big fan of Dragonball Z. The only role Dragonball Z plays in is sonic characters sharing somewhat the same personalities as familiar characters from Dragonball Z. Ian Flynn was going by his possible thoughts and theories of whom he thought could be the parents of Silver and he went originally, by Amy and Shadow. However, Videogame creator of Shadow The Hedgehog, Takashi Iizuka confirmed that Shadow and Silver are not related. Ian Flynn was shown proof of Takashi stating so and his reply was Yup. Which totally disregarded his theory of Amy and Shadow being the parents to Silver.
I've seen Dragon Ball Z a lot. And the Sonic characters hardly have personalities that are completely the same as the Dragon Ball Z characters. Even Shadow's and Vegeta's personalities are way too different to be the same.