There is a Maryland, Calendar of Wills, 1635-1743 on Ancestry.com:
Name: Thomas Lucas
Occupation: Planter
Will Date: 18 Oct 1721
Will Place: Prince George's, Maryland, British America
Probate Date: 26 Feb 1721
Death Year: Abt 1721-1722
Text: Lucas, Thomas, planter,Prince George Co.,18th Oct., 1721; 26th Feb., 1721-2. To sons Thomas and Charles, daus. Mary (wife of Wm. Scott) and Eliza. (wife of Geo. Moore), is. each. To wife Dorothy, extx., 250 A. dwelling plantation —– during life; at her decease to son John and hrs. He to pay to his bros. Samll. and James 500 lbs. tob. each. Sons to be of age at 18. John being 12 yrs. 20th last June, James 8 yrs. last Feb., Samuel 4 yrs. last Sept. Personal estate, after wife's thirds are deducted, to all child. by sd. wife, viz. Susana, Sarah, Jane, John, Mary, James, Samll. and Eliza. Test: Edward Williot, Ninion Willett (Willcot), James Cross. 17, 147.
Original Source Name: Land Office
Original Source Location: Annapolis, Maryland, USA
Original Source Series: Will books
Original Source Book: 17
Original Source Page: 147
According to this (I did not know how to add it since there is not an image to add, just the synopsis) Samuel was 4 the last September. This document was written in October 1721. That means Samuel was 4 a month earlier than this was written or Thomas forgot Samuel had had another birthday since then. So, since Thomas was 68 or so when he passed away, he would have been about 64 when Samuel was born.....If my calculations are correct, I am not sure how to fix it so the inconsistency does not show up anymore. I am also leery to make any changes since I heard I made a mistake a while back..
Does this sound correct to you?
Mary Ann (Huffman) Solbrig