John Gill Commentary 2 Chronicles 11:18

"And Rehoboam took him a wife, Mahalath the daughter of Jerimoth the son of David, [and of] Abihail the daughter of Eliab the son of Jesse;" — 2 Chronicles 11:18 (ASV)

And Rehoboam took him Mahalath, the daughter of Jerimoth, the
son of David, to wife
Of which son of David we nowhere else read; perhaps he might be the son of one of his concubines, or he might have two names:

and Abihail the daughter of Eliab the son of Jesse ;
who was David's eldest brother. (1 Samuel 17:13 1 Samuel 17:28) . She must be a granddaughter or great-granddaughter of his.