In a stroke of luck, Thomas Kirkwood's will is located! Thomas wrote his will on 10 November 1722; it was proved 26 October 1723.
Thomas named the following children: my eldest son, Ian... eldest daughter, Sally... sons Harper & Thomas... daughters Lucy Ann, Mary, Sarah & Ann... my unborn child... my wife, Sarah. Wife Sarah & eldest son, Ian named executors.
So, here we have it, the Kirkwoods had: Ian [b. 1702], Sally [b. 1704], Lucy Ann [b.1705], Mary [b. 1711], Harper & Sarah [twins, b. 1713], Thomas [b. 1715], Ann [b. 1722] & James [b. 1723, shortly after his father's death]
Even though the couple had nine children, there are gaps [1705-11 & 1715-1722] that would allow for the births of children who did not survive until 1722.
How did you do?