Below are the openings of the recent sequel/franchise films and all the second films have opened less than the first one if we take into account inflation. A second film is made because it holds some brand value with the audience which will lead to a better initial of the second film especially if the first did not open which is the case with all the films below.
Rock On!! (2008) - 1,66,00,000 (400 screens)
Rock On 2 (2016) - 1,98,00,000 (1400 screens)
Eight years later with 1000 screens more but just 30 lakhs nett more collections

Tum Bin (2001) - 15,00,000 (90 screens)
Tum Bin 2 (2016) - 65,00,000 (1100 screens)
The box office has change a lot over the 15 years gap between the two films but its safe to say the opening of Tum Bin is better even though low.

Force (2011) - 4,53,00,000 (1450 screens)
Force 2 (2016) - 5,25,00,000 (2250 screens)
Five years later and 800 more screens but collections just 75 lakhs more

Kahaani (2012) - 2,91,00,000 (1100 screens)
Kahaani 2 (2016) -???
Remains to be seen if this can double up or close to the first film which opened poorly

The worst sequel of the above is no doubt ROCK ON 2 unless KAHAANI 2 is a shocker. The screen gap between ROCK ON!! (2008) and ROCK ON 2 is insane and its just ridiculous for collections to be so close.