I am very sorry to hear about your sister. And its understandable that youd be worried.
A brain aneurysm is a balloon-like pouch that sticks out from the wall of an artery inside the brain. If it bursts, blood pours into the brain, and that can be fatal. But most such aneurysms never burst.
About 1015 million people in the United States have them. About 30,000 rupture each year. The risk increases with age and the size of the aneurysm. Where in the brain the aneurysm is located is another factor.
Brain aneurysms do run in families. Theyre also associated with several diseases, including polycystic kidney disease and Ehlers-Danlos and Marfans syndromes.
Noninvasive imaging tests like magnetic resonance angiography (MRA) and CT angiography (CTA) can find them with reasonable accuracy. The problem is that predicting whether an aneurysm is likely to rupture is difficult. Also the available treatments to prevent rupture some of which involve surgery and other procedures within the artery are risky.
So, even if there is a small aneurysm, is the risk of treatment greater than the risk of rupture? Often its hard to say.
In general, though, experts recommend that people be screened for brain aneurysms if two or more first-degree relatives (parent, sibling, or child) have them. You have only one first-degree relative who is known to have an aneurysm. So strictly speaking you dont need screening.
On the other hand, your sister was young and died from a ruptured aneurysm. And I gather you and other close relatives apparently havent been screened. So there is no way of knowing if another family member might have an aneurysm thats gone undetected. However, if you have a large family and no one else has had a ruptured aneurysm, then your risk is likely no greater than the average person.
But this is a complicated issue. And I recommend discussing it with your doctor.