Susan James was bound to be a brother/nephew to Michael Coward Jr.
I say this because in 1830 a James age 15-30 was located next door to Michael on the census in Marlboro, SC. If Samuel was dead as I believe he was then James would be male head of household since his mother would not inherit as a female could only stand in trust if no male adult relative was available and there was no will.
Michael is listed on Wikitree and the age shown for him in the 1830 census is 30-40. Now, in 1860 Caroline and her children including James Spencer in the home of Richard Welch and wife, Susan. They are in their 20's and Caroline is shown as age 22. Also, in the home are Charles Bone age 16 and Catherine Bone age 17.
All of this information would indicate that Michael and James Spencer are 1st cousins who have inherited land by 1860 very close together in Marlboro, SC. or they may be brothers. 15 to 30 is a broad age when you consider a male was an adult and able to homestead at age 21. Obviously if Michael is a Junior then his father was a senior. The Coward's married into the Smith, Bone, and Welch families who live near each other and settled near each other in Marlboro County. If you want the two census records from 1860 one showing Caroline and the other Michael Jr send me your e-mail and I will pass them to you. I downloaded the page so you could see who the Smith Family between the Cowards are.