Are middle kids treated differently?

Well, I'm not 100% sure, but I think I know what your parents mean...

When the baby is born, you, as the older child, will most likely have more responsibility. I'm an older sister, and my little brother is (very) annoying sometimes, but my parents expect me to do more chores, keep my room tidy, help my little brother, etc. Warning you: It can get annoying, but patience is key. Besides, once you finish school, you can move out and it won't even matter! :D (hehe, just kidding.)

They may also be referring to how when the baby is born, they will be busier! Trust me, a baby is a full-time job. Lemme give you the 411: Feeding him/her. Changing his/her diapers. Burping. Doing all of this whenever him/her needs it. 24/7!

You most likely will be expected to be more independent. Not like, cooking all of your own meals, driving yourself to school! But maybe, doing your homework without being asked, getting ready quickly, etc.

That's just my guess! Congrats on your new addition! :) xx