Jamieson, Fausset and Brown on 1 Chronicles 7:14-15

14-15. The sons of Manasseh--or descendants; for Ashriel was a grandson, and Zelophehad was a generation farther removed in descent (Nu 26:33). The text, as it stands, is so confused and complicated that it is exceedingly difficult to trace the genealogical thread, and a great variety of conjectures have been made with a view to clear away the obscurity. The passage [1Ch 7:14, 15] should probably be rendered thus: "The sons of Manasseh were Ashriel, whom his Syrian concubine bare to him, and Machir, the father of Gilead (whom his wife bare to him). Machir took for a wife Maachah, sister to Huppim and Shuppim."