Sorry, both treated exactly the same way.
The only way that will happy is if they are both not confirmed, ie both travelling standby, so yes that can happen. Same rules as subload apply.
If your confirmed you don't go to the staff travel desk and can check in at home or the AEL like any normal passenger. A 2nd yr SO with a confirmed 11Y will get on before a standby 11B with 30 years of service.
More often than not you will also get confirmed with 11B over 11YW during busy periods as YW is normally full while J has seats.