Tbf, some folks only ever had fights with siblings. And then there's the folks who never had siblings and only think of the real tame "fights" you see in things like games and shows... then there are plenty that have a genuinely good relationship with their siblings. It's a whole mix bag, and I can definitely appreciate a breath of fresh air that is siblings that got eachothers backs and like hanging with eachother with the occasional ribbing instead of constant squabbling lol.
I'm just thankful it's not yet another failed garbage tsundere... it's so rare people do a tsundere that isn't genuinely outright insufferable lol and it seems to constantly be a sister character that ends up being the tsundere that just constantly argues and fights with the MC. Over used trope + poorly used trope combo makes it so bad. Now I do have to say, I can enjoy a brat and a well done tsundere that isn't souly there to just be annoying. But gods am I thankful Ash is a damn good sister type instead of a garbage tsundere.