Yes, I agree these Steuarts probably aren’t your Stewarts/Stuarts. What have you found on this Col William Stewart you mention?
In the meantime, here’s another of the Steuart brothers’ wills…
Crossle Will Abstract (FindMyPast):
Colonel John Steuart of the City of Dublin
To be buried in the vault under the communion table in St Mary's Church.
Marriage settlement dated 19th and 20th Apr 1722 ratified except what applies to my daughter.
Settlement of Co Carlow estate on son William prior to his marriage to Ann, daughter of Sir Richard Butler, Bt.
Wife to live in dwelling house in Stafford Street.
Already paid £4000 marriage portion with daughter Mary, so William's Meath estate to be free from incumbrances.
Son-in-law Walter Weldon Esq, married to daughter Mary.
Brother Admiral James Steuart.
Admiral Dockling and his family.
Sister Gregory and her family.
Wife, brother James, and son William to be executors.
Dated 23rd Feb 1757.
Witnesses Edward King, David Steuart amd Dens/Danl Kane.
Probate grated 1 Feb 1763 to son Wm Steuart.