I have been thinking about the 1857 newsarticle in which it is reported that Martha Carson Boyd's mother is Mrs. McKeown. This is only true if her parents were John Boyd (as per her marriage to William Young in 1865) and Jane Hay. John and Jane Hay were married in 1837 in Carrickfergus, and John Boyd must have died before 1855 when Jane remarried to Matthew Keown aka McKeown.
So when Martha got the license in 1862, it was from her stepfather Matthew. Makes sense.
We need John's marriage to see if it names his father, or his birth abt 1810 (same time frame as Samuel Carson Boyd's son John but I don't think it is him) or his death 1852-1855.
Another possibility is that John and Jane separated.
Presuming John died, perhaps there is a record of his death, or a newspaper notice or writeup.