Is it mean to rather give clothes to the goodwill than a family member?

I usually give my old, too little clothes to my niece. We are the same height, but she's skinny. I hate when I give my NIECE something, then see my sister wearing it.

And these items (shirts) DO fit my niece..my sister also wears actual kid clothes and I dont understand why. Yesterday she work a pink fringe shirt with 3 feathers on it. Obviously a kids shirt and probably my neices😒

Goodwill, here I come 🏃