(51) The son of Abiel.--For "son" the commentators mostly agree we must read sons. Kish and Ner, we know, were both sons of Abiel. (See 1 Chronicles 9:35-36, where, however, the father's name is given as Jehiel.)
Verse 51. - The son of Abiel. There can be little doubt that the right reading is sons, and not son. We thus get an intelligible statement - "And Kish the father of Saul and Ner the father of Abner, were sons of Abiel."
14:47-52 Here is a general account of Saul's court and camp. He had little reason to be proud of his royal dignity, nor had any of his neighbours cause to envy him, for he had but little enjoyment after he took the kingdom. And often men's earthly glory makes a blaze just before the dark night of disgrace and woe comes on them.
and Ner the father of Abner was the son of Abiel; this Abiel was the father both of Kish and Ner, and the grandfather of Saul, see 1 Samuel 9:1.