I believe Network18 is strictly the news division, which has nothing to do with the merger with Disney Star, but instead has JVs with CNN and CNBC. TV18 on the other hand is the company that owns not only Viacom18 but also AETN18, which owns History TV18. Out of these only Viacom18 is merging with Disney Star. Ultimately all these companies are owned by Ambani’s Reliance. I might be wrong on the specific structure and ownership, but this is my general understanding.
Its also from TV18 Subsidiary AETN 18 . @Rajkumar Bro its also Part of TV18
For Info TV18 also has another Subsidiary GREYCELLS18 Media PVT LTD which runs a Educational satellite Tv channel named as "Topper" . Its also Part Of Tv18 .