Throughout all their childhood Luffy had been the one to follow. It was always Ace and Sabo who were stronger, faster, brighter, but it didn't really matter because they were happy. Two older brothers who protected each other and their younger brother too for he was still so weak. He was their sunshine though, their freedom and happiness, even when they hadn't seen it at the beginning.
Now Sabo was the one to follow. And while he could keep up, yes, he wasn't the only one protecting any more. Luffy had a crew to look out for. Eight brilliant and strong people who seemed to constantly disrespect their captain yet followed his every order without hesitation or question.
Sometimes Sabo wondered what Ace had thought of the Straw Hats. Had he found them suiting for their little brother or did he have doubts?
There was "Dead-Bones" Brook, an amazing skeleton musician. He was older than all the rest, but no-one seemed to mind. Luffy obviously found him simply amazing and Sabo couldn't help the small smirk that crossed his lips at another skull-joke.
Then there was the carpenter "Cyborg Franky". An interesting man with even a more interesting stile. The blue-haired man seemed to have a strong aversion to trousers and an almost unhealthy obsession with cola.
Robin, whom Sabo and Koala knew from her stay with the revolutionaries, was as mysterious as ever, but there seemed to be a soft and amused look in her eyes whenever she was in the company of her crewmates that the blond man hadn't seen before. She reminded him a bit of Ace though.
Chopper was adorable. There was no denying though that he was one of the best doctors Sabo had ever laid his eyes on. He was childish and timid, but whenever someone (mainly Zoro) tried to defy his orders, the young reindeer fierce enough to make them listen.
Sanji was a romantic. It was funny to watch how he tried to fuss over Koala, only to be shot down times and times again. The ladies of Luffy's crew seemed to enjoy it and use it to their advantage. Sanji had a tougher side too, as Sabo found out. He was fierce in protecting all of his crewmates, be they male or female.
Usopp was Luffy's childhood, as far as Sabo understood. He was fun and kept the mood light even when times were hard. Luffy and Chopper obviously adored him and the others seemed to have some kind of a soft spot for him too. He was brave in his own cowardly way and he made everyone smile ever so often.
Nami was exactly what this crew needed. She was fierce and kept the boys in line. She also seemed to have a knack for understanding the strange weather of Grand Line. Sabo was absolutely sure that Luffy wouldn't have gotten anywhere without her help. No other seemed to be able to keep the young Captain from getting them all lost on the strange seas.
Lastly there was the swordsman Zoro. He seemed to sleep or train most of the time and interact little with the others unless he fought with the cook, but Sabo found that he always seemed to keep an eye on everybody. He also understood Luffy, a feat even Sabo and Ace had never completely mastered.
Sabo trusted them though. He knew that when the time came he had to leave again these people would too anything to keep their captain alive as would Luffy.
And as much as Sabo didn't want to admit it, while his brother loved him very much, he didn't need him anymore, hadn't needed Ace either.
That didn't mean that he would stop looking after his baby brother. Needed or not, extra protection was never bad and Sabo couldn't even imagine what it would feel like if he lost another brother. Ace would beat him up in the afterlife for failing when he got there.
Sabo wasn't too worried though. While Ace had had Whitebeard to protect him, no-one could match Luffy's determination to live and protect. The Straw Hats would be fine and accomplish all their dreams. And if Luffy ever ended up on an execution platform he too had many friends who would come to help him. He had saved the lives of many important people and he had Sabo and Ace (who undoubtedly was keeping an eye on him from the afterworld) to watch out for him.