Eleazar was a common name among priests during this period. The fact that he was not killed in his care-taking duties suggests that he was a Levite. Reference to Abinadab will be made again in 2 Samuel 6:3, when the ark is moved to Jerusalem. He is said to have two other sons, Ahio and Uzzah. Most likely they were his grandsons, given the time that had passed since the ark first came to Kiriath-jearim.1
1 And the men of Kiriath-jearim came and took up the ark of the LORD and brought it to the house of Abinadab on the hill. And they consecrated his son Eleazar to have charge of the ark of the LORD.