When my brother joined my world, we´ve seen each others custom/import skins as Steves, but when we opened inentory or look at our hand it was our custom skins.
When i changed my skin to the skin you can make in minecraft,
he saw me normally as that skin, and when i changed back to my custom/import skin, he again saw me as Steve.

(In his phone i looked as Steve and he was normal, and in my phone he was Steve and i was normal)

It´s realy annoying and unsettling.