Wait, you're getting this from a book? Unless Peter's 'sister' was introduced within the past year, he doesn't have a sister in comics.
Ock doesn't have adamantium arms outside the Revenge plotline. What can GG do? He has enough firepower to decimate Ock. Octavius can stop bullets with his arms, not rockets, missiles, or a barrage of pumpkin bombs. Ock cannot even touch Goblin when he's on his glider.
Doctor Octopus is not stronger, not by any means. Green Goblin is stronger than Spider-Man.
In comics, Green Goblin is strength level slightly weaker then Spider-Man's. Each of Dr. Ock's arms can lift three tons, so their strength level counted together is 12 tons. So he is couple of tons stronger then Spider-Man
From Spider-Fan.org
(Doc Ock) A brilliant engineer and inventor, he is also a superb strategist and a charismatic leader.
Yeah, I dont know does that mean battle-wise, but anyway.