Re your summary, John's son Ninian is the only executor. His wife and William Stewart are tutors to his younger children.
Stewart of Kilchattan, according to the list of debts awin in, owed John Stewart £1,333 6/8d. That is exactly equivalent to 2,000 merks, a merk being 13/4d. That tallies with the legacies where he gives two of his children 1,000 merks each from Kilchattan's debt.
I think it says all three were executors and then a few lines later says his wife and William were to be tutors to the children. On the first page it refers to Ninian Stewart being the executor "acceptour" which I took to mean accepted, as in the other two renounced their entitlement to the role?
I didn't know £1,333 6/8d was 2000 merks, so yes that tallies nicely. I see Christian Stewart was given 400 merks of the money owed by her brother (not named). Siblings William and Elizabeth Stewart were given 100 merks each of the same money. That matches the 600 merks owed by the grandson John Stewart. I therefore conclude that Christian and John were siblings, and both were children of the late James Stewart of Ardinho.
This fits with the version of the family in Paul's Scots Peerage which says James Stewart of Ardinho was a minor in 1612, but he seems to have been succeeded by his son John Stewart by 1630.
