Username changing in profile when i dont want it to

when i made a new profile for the snapshot i saved it with my username.
after my brother plays minecraft i play. but when i select my profile my brother is still logged in and i have to change accounts every time what i didn't have to do before.

1. create 2 profiles, 1 with one user en 1 with another user.
2. play with the first profile. (so you play the first user)
3. close minecraft & launcher.
4. start launcher and select the other profile.

then it should be logged in by the first player instead of the second one.