BRISTOW, John King, 1814-1881; Lane Co., Oregon

I have a John King Bristow and a John Kennedy Bristow as sons of Elijah Bristow and Susannah Gabbert. Both born 26 Mar 1814 in Tennessee; John King's death as 28 Jan 1881 in Lane Co.,Oregon; and John Kennedy's death as 1887 in Eugene, Lane, Oregon.Both married to Mary A.; however, for John Kennedy I also have him married to Susan Conger and Emeline Harriet Hatch.They have to be the same person; however, I would like to know where the middle name "Kennedy" came from (Find a Grave shows it as KING), and would like to know if John King was married to Susan and Emeline?