I have a two cm. cyst in my frontal left lobe of my brain. my grandmother had an anyurism and stroke. am i at a higher risk than most because of this?

Probably not: The 2 cm cyst in your head/brain is presumably an arachnoid cyst and is not itself a risk factor for aneurysm. There is likely a hereditary component to some aneurysms, and often screening is done for people who have a first degree relative (i.e., parent, sibling, child) with an aneurysm. Having a single grandmother with an aneurysm likely does not increase your risk much if at all.