Autoselect a value or autounselect a value

Hey everyone! I have this multi select, that I’m using with Select2.
<select class="js-example-basic-multiple" name="roles[]" multiple="multiple" style="width: 260px;" required> <option name="add_or_edit_user[role_one]" >One</option> <option name="add_or_edit_user[role_two]" >Two</option> <option name="add_or_edit_user[role_three]" >Three</option> </select>

Currently it works just fine, but I wanna add a functionality where if I select, the role number three, I also want to auto select the role number one. This is because role number three is attached to the first, so role number three cannot be by itslelf.
Also, I want to add that when you unselect the first role, if the third role is seleccted, it will be automatically unselected.
Thanks beforehand! If anyone can help me I’d be delighted.