my cat has brown spot over eye / under ear

[foxykairi]

my cat is fully healthy and i haven't realized any behavioral changes recently. she's always had less hairy spots over her eyes and she's always had these brown spots. i never really bothered about them because my cats always appeared healthy. i included a video for you all to see. now i was overthinking a bit and i'm scared it might be anything of concern, and i never did anything against it that's why i'd like to ask the question in this forum, if these brown spots are worrisome or not? she has a fully black twin sister who has the same bald spots but her skin is white under it.

[Mollycat]

Thin hair is normal in this area in front of the ear, and brown stain marks are very common. Most of my cats have had these as they aged, Molly has a small one now. I've never known them to indicate any trouble but I don't know what they are.