Joseph, born in neighboring Southborough the son of Joseph Arnold of Reading, Middlesex, Mass., who became known as the blacksmith of Grafton, Worcester County, Mass., and Dorthy Hartwell of Concord, Middlesex, Mass, came to Marlborough in 1762 to reside with Mary Sherman (widow of John). Joseph also took up the trade as a blacksmith. On 10 December of that year in Shrewsbury, Worcester County, Mass., he married Lydia Fay, who was also born in Southborough to a prominent family on 21 May 1743. She bore him 5 sons and 4 daughters. Lydia died in Marlborough on 19 November 1776 at the height of the Revolutionary War. During the War, Joseph Arnold was a 2nd lieutenant in Captain William Morse's 8th Company, Colonel Ezekiel Howe's 4th Middlesex Co. Regiment and he was on the list of officers of the Massachusetts Militia, commissioned on 5 July 1776. Note that Captain William Morse left Marlborough with a company of 52 Marlborough men on October 5, 1777 to join the army at Saratoga, and arrived there October 17th the day Burgoyne surrendered. Joseph also served as 1st lieutenant, 8th Company in Colonel Cyprian Howe's 4th Middlesex Co. Regiment and was on the list of officers of Massachusetts Militia commissioned 4 May 1780. Colonel Howe was from Marlborough (Find-A-Grave Memorial No. 70999179). From his second wife, Persis Warren born 9 Apri 1741 in Marlborough whom he married in 1776, he had three children, Molly b. 1778, Levi b.1779 and Aaron b. 1781, about whom relatively little is known. Persis was the daughter of John and Zipporah (Brigham) Warren of Marlborough, Middlesex, Massachusetts. The 3xgreat-grandparents of Lt. Joseph Arnold were Nicholas b. 1550 and Alice {Gulley} b. 1553 Arnold from Somerset County, England. He shared these ancestors with the infamous & controversial Gen. Benedict Arnold, making them 4th cousins. One can only speculate whether this distant relative had any bearing on the life of Lt. Joseph Arnold. Benedict Arnold moved to London in 1782 and eventually died there in 1801 at age 60. Joseph had died in Marlborough five years earlier at age 58.

Joseph's father, Joseph Arnold of Grafton, signed the following deed in the son's favor in 1763:

1763 Worcester County Land Deeds volume 46 page 486
Know all men by these present that I Joseph Arnold of Grafton in the county of Worcester and in his Majesty’s Province of the Massachusetts Bay in New England Blacksmith in Confirmation of the Just Sum of Fourteen Pounds Lawful Money to me in hand paid Before the Deliver hereof by Joseph Arnold of Shrewsbury in the County & Province aforesaid Blacksmith have Given, Granted, Bargained ,,, and do by these Presents give, grant Bargain …. ….. Convey & Confirm unto the said Joseph of said Shrewsbury his heirs & assigns forever a Dwelling House & two Blacksmith Shops in said Grafton the house and one Shop Standing Near the Meeting house by the Rev Aaron Hutchinson on Land Leased by Nathaniel Sherman Innkeeper in said Grafton …..Said Joseph Arnold of said Grafton the other Shop is in the Northwesterly part of said Grafton near the house where the Grantor now dwells together with the whole of all the Smithing Tools & Instruments as the Bellows, Iron Stakes hammers shoeing tools & set of Shovel Tools with every other Articles and Tools said Grantor makes use of in the Smithing Business to have and to Hold the said Grants and Bargains Premises together with all their appurtenances free and clear of all incumbrances Whatsoever to the Said Joseph Arnold of said Shrewsbury his heirs & assigns as a good and Save Estate forever and the said Joseph Arnold the above Grantor for himself his heirs Executors and Administrators do Covenant and Engage the above _____ Premises to Said Joseph Arnold of Said Shrewsbury his heirs and assigns against the Lawful Claims of any Person or Persons Whatsoever forever hereafter to Warrant ___ and Defend by these Presents & Furthermore Joseph Arnold the Aforesaid grantor for himself and his aforesaids doth by all Presents Leafe & Confirm unto Said Joseph of said Shrewsbury this aforesaid for the sum aforesaids one acre of Land be the Same more or Less on which aforesaid conveyed House Stands & is the whole of the land leased as aforesaid by said Sherman and said Joseph of said Shrewsbury or his aforesaids is to hold, Possess and Enjoy & improve the aforesaid Leased Land according the Butts & Boundarys and During the whole time and that is leased by said Sherman to said Joseph of said Grafton for and that without let hinderance or Disturbance of any Kind Whatsoever & In Witness to all above Written Joseph Arnold of said Grafton hath hereunto set his hand and seal the first Day of November a.d. 1760 and in the first year of the Reign of his Present Majesty George the Third of Great Britain France & Ireland King to Joseph Arnold ‘
Signed Sealed and Delivered in Presence of Timo Paine William Paine
Worcester June 22, 1763 Joseph Arnold acknowledged this Instrument to be his act & Deed Exam Timo Paine Jus _____Rice June 22, 1763
Accordingly Entered and Examined Timo Paine, Reg.