Again, not an expert, not my area of practice, but... the wife has worked in probate for almost 15 years (and has a consulting business related to probate).
I think the term "disown" is misleading. There's nothing, technically to "disown". But - and this is why it's impossible to give a definitive answer with the information given - each state has rules for the intestate distribution of assets (this is a lawyerly way of saying "where does your shit go when you die, and you do not have a will"). There are scenarios where a sibling (or siblings) could receive all or part of your estate. The most obvious is when you and your sib are, literally, the last of the Mohicans.
Generally speaking, you can only circumvent that prescribed distribution by having your own appropriately executed (signed) and witnessed (if required) will. (Note: you mentioned SIBLINGS; in some jurisdictions you can't always disinherit spouses, and - notably Louisiana - you can't always disinherit children, at least entirely).
Your best bet is to be clear with your intentions, put them down on paper, clearly (sorry, don't mean to be a dick about that, but humans - myself included - have a tendency to THINK they're clear and they're anything but). Best is to have a lawyer read it, besides that, have a disinterested party (meaning, someone who isn't inheriting or isn't in a position to inherit from the will) read it and tell you what they think it says.
Word to the wise: if you have something in particular that you want passed (or not passed) to someone, specifically call it out, and if it isn't something like a car, that you use every day, put it somewhere safe, like a safe or a safe-deposit box. Alternatively you might consider putting any major asset in both persons' names (though I wouldn't do that at your age unless you are in extraordinary circumstances, like deploying to combat or have major surgery or major illness). Things like "lockets", "rings", and "bracelets" have a way of finding legs in situations like this.
Last thing: DO NOT ASSUME YOUR KIN WILL ACT RESPONSIBLY OR MATURELY AFTER YOU PASS. I have too many stories of families showing true colors after a death in the family. My own mom's sister hasn't spoken to her in about 25 years because of the disposition of a shitty Buick Regal after their mom passed. My wife's father and brother haven't spoken to several of their relatives after their sister passed, and when they went to the house to help distribute her stuff, the house was literally empty. All the pictures, all the jewelry, all the mementos... gone.