Sounds like our middle school DD's are dealing with a lot of the same things! Our DD10 has an older sister (both now in same grade since younger DD accelerated)who is "perfect". Teachers say it, other parents say it - poor DD10 has accepted that as truth. Older DD makes friends easily, is organized, loves sports, and is just a pretty easy kid to be around. Older DD wins at "life skills". DD10 is sarcastic and touchy so people miss the amazing humor and kindness that lies below the surface(she's good with toddlers and babies, great comedic writer). It makes for a big sibling rivalry. We have tried to keep them separated in sports and other after school activities, but it is hard because they are close in age and both girls - unlike your 2.
I don't think I have any advice so am just giving a big nod and saying "Have the same thing going on over here!" We keep working at it and trying to help them work on their own gifts. Exhausting, yes.
