Is a right common iliac artery aneurysm genetic? Should siblings and/or sons be checked / have a scan?

It can be. About 20-25% of aneurysms of the aorta and iliac arteries are inherited. A simple arterial scan in a vascular lab of first degree relatives once over the age of 50 is helpful to pick these up.
Probably not. Did parents have troubles with aneurysms? Ultrasound can detect, follow many noninvasively in the thinner folks. It may require ct in larger persons. The iliac arteries are deeper vessels. Screening family is reasonable.