You've already accepted that the oldest sibling is going to acheive certain things before you. They'll graduate first, be the first to drive, and likely be the first to marry. But God forbid the younger sibling overtakes you on any of the big things. You've got your work cut making sure everything happens in the right order. Nothing would feel worse than having the younger sibling achieve more than you at a younger age. It's a constant stress trying to keep ahead!