Responses
It can never be incest since Luffy and Ace aren't blood related but only raised as brothers.
You are right. Technically, they are not blood related. I'm sorry, I have a sister with who I'm not blood related eighter, because one of us is adopted, so I usually think about brothers that grew up as real familly the same way, even if they are not blood related. At least, to me, all my sisters and brothers are equally important, even if some of them have my blood and others not.
This is not Zoro x Sanji, it's Luffy x Zoro and Luffy x Ace. If you don't like incest or hard yaoi, don't read it.