Answer
Yes, it's possible that Nabonidus was part of the Sargonid dynasty. He was the last king of the Neo-Babylonian Empire, and his mother was a daughter of Sargon II, the founder of the Sargonid dynasty. However, there is some debate among historians about whether Nabonidus was a direct descendant of Sargon II or if he was related through a different branch of the family.