Oh, now I'm really giving away my age, eh? [Mischievous twinkle to his eyes and drops his voice again just a little. He has no intentions of riling Ace up further with mentions of his not!Dad.] I get along better with Rayleigh. [Shamelessly headcanon/fanon-ing this.] He's been a good ally about the Fishman Islands and dealing with slavery. He keeps an eye out for any of the youngsters who go up to Sabaody in spite of the danger, so if it weren't for him we'd have a lot more problems. [Since Sabaody is strictly No-man's land, and the emperors can't deal with it.]

Plus it's probably the first-mate thing. And he finds Shanks and Buggy as irritating as I do, maybe more, since he had to deal with them as cabin-boys.