John Gill Commentary 1 Chronicles 26:10

"Also Hosah, of the children of Merari, had sons: Shimri the chief, (for though he was not the first-born, yet his father made him chief)," — 1 Chronicles 26:10 (ASV)

Also Hosah, of the children of Merari, had sons Who was a fellow porter of Obededom's at the ark, (1 Chronicles 16:38) .

Simri the chief (for though he was not the firstborn, yet his father made him the chief) ; the firstborn being unfit for service, either through want of an intellectual capacity, or of strength of body, or through some defect or another; according to the Syriac version, he was dead; so some understand the words, he, the father, had no firstborn remaining or living.