John Gill Commentary 1 Chronicles 7:16

"And Maacah the wife of Machir bare a son, and she called his name Peresh; and the name of his brother was Sheresh; and his sons were Ulam and Rakem." — 1 Chronicles 7:16 (ASV)

And Maachah the wife of Machir bore a son, and she called his
name Peresh; and the name of his brother was Sheresh
He had both these sons by her:

and his sons were Ulam and Rakem ,
that is, either the sons of Peresh or Sheresh, the nearest, as Kimchi observes.