Summer Trip with Jake’s family

[Freesub]

I grew up with a brother one year younger, so naturally we saw each other naked all the time.
If it was a sister, I wonder how it would have been different. Would I have grown up to be comfortable around a girl in minimal clothing?
Would I have been comfortable being seen coming out of the shower as a teenager? I'll never know, but I've wondered about that.
What is the percentage of similar aged boy/girl siblings who don't mind getting naked in front of the other?

If they are twins, it's usually much higher than for those with an age gap.

In my experience it is usually Twins>Brother is Older>Sister is older

But if you say just underwear, I would say it is Twins>Sister is older>Brother is older