(If I am not mistaken, Animal planet, Discovery, TLC, MTV, VH1, Travel channel, Sci-Fi, comedy central, cartoon network and a few others are all owend by the same parent company (Viacom)..which is why they always advertise for each other...and is why Disney parks are never in any of their shows...)
No- Viacom does not own Discovery Channel
Viacom ownes Infinty Broadcasting Company, Nick, MTV, VH1, Comedy Central, and CBS
Cartoon Network is an AOL TIME WARNER COMPANY
Discovery owns- TLC, Discovery Health, Animal Planet, Discovery Channel, Travel Channel and a few others but do not own Discover Magazine Buena Visita Publishing does which is owned by Disney.
Disney ownes- ABC, ESPN 80%, Disney Channel, ABC Family, I think 37% of A&E and the History Channel.
And Disney is advertised on other channel and Magazines they don't own.