Yes, I wouldn’t be as worried about sticker shock if your parents already put your sibling through Duke - clearly they understand what it costs. But the decision about how much to stretch financially for undergrad also depends on your post-college plans. If you want to study engineering and go straight into a well-paying job, that’s quite different from if you want to go to med school or law school. Discuss with your parents where things will stand, financially, by the time you graduate, and whether that aligns with your career goals. It makes no sense to blow all your resources on a “dream school” and then not have the financial resources and freedom to do what you really want to do with that degree when you get out. So, it depends.
What other schools are you interested in, besides Duke?
What is your home state - is your state flagship both an admissions safety and a financial safety that you’d be satisfied to attend?
Are there match and safety schools on your list that have non-restrictive Early Action? (Just based on typical overlap schools with Duke, possibilities might be URichmond, UMiami, Tulane, Miami of Ohio… but without knowing what you want to study and what your other criteria are, I’m just guessing.) It could be nice to have some other decisions besides Duke rolling in early, just in case.
Also, do you have an ED2 school in mind in case Duke doesn’t work out? A few possible examples would be Emory, Wake Forest, William & Mary, WashU… but again I’m just spitballing, without knowing much about you besides your love for Duke.