Sources & Information:
There has been some mix up on actual name of wife as Mercy Nye or Mercy Burgess. Could Mercy Nye have married a Burgess and then Matthias Ellis?
Col. Harry H. Ellis states that Matthias married Mary Burgess, not Mercy Nye as was once thought. Mrs Freeman (Alice) G. Ellis, 122 Shrewsbury Street, Holden, MA. 01520. Matthias Ellis received considerable inheritance from his maternal grandfather, Edmond Freeman, as a reward for caring for him in his old age.
By a deed dated February 24, 1678, Edmond Freeman, the eldest, of Sandwich conveyed to Matthias Ellis "my grandson.....as living with me until he came unto man's estate, being a support unto me in my old age and weakness; wherefore I do give unto him his heirs and assigns all that my now dwelling house and orchards being in Sandwich........".
Matthias with brothers Freeman and Manoah took oath of allegiance in 1681. He and brother, Mordecai, are listed as Sandwich Freeman in 1702. In 1705 he was named to a committee to act as agents for the settlement of bounds between Mashpee and Sandwich.
Lt. Matthias Ellis was granted 150 acres in consideration of services rendered in the expedition to Port Royal, especially guarding artillery at great hazard of his life. This award was made in
1739 and Matthias then about 82 years of age. He was being rewarded for his bravery during the conquest of Port Royal which took place under command of Sir William Phipps during King Philip's War, or could have been for part in the reduction of Port Royal in 1710.
Matthias wrote his will November 13, 1744 which was proved October 4, 1748 and reads: ".....to my loving wife Mercy the use and improvement of the Westerly End of my dwelling house both lower and upper rooms and the leanto on the back side of it and the cellar under it .... and also the use of my....little orchard...as long as she remains my widow. Also so much of my household goods as she shall think necessary and convenient for her use...during her said widowhood... to my son Joel....the two half lots in the woods that were formerly my son John's and also my sheep pasture lot in that tract called Snake Pond sheep pasture lots. I do also give him half of my apparel, cutlass, belt and cane and twenty pounds Old Tenor to be paid within one year after the decease of his mother by... to my son.Item: his Books. 4 cowers and other, young calves, 1 bullock, 1 bullock in the woods that cannot be found, 1 horse, 10 sheep and 6 lambs, 5 swine that are small ones and 1 piece of a barrel and pike, 3 chairs, tacking and old iron, some timber for a dwelling house At 30 ft. and 18 ft. wide, 18 bushels of corn and some iron things for lead, 1 Cobber staying At Mr. Freeman's house.
Signed Richard Bourne
John Smith
Thomas Tobey

A Similar inventory submitted the same date for John Ellis, Jr. by Mistress Elizabeth Ellis was witnessed by the same three as above. One theory on the relationships not heretofore mentioned is that the landholders John Ellis Sr. and John Ellis Jr. in 1658 were in fact father and son - Lt. John being the son and that Lt. John Ellis and his son John Jr. died in King Philip's War.

Matthias took part in the expedition to Port Royal under Sir William Phipps during King William's War (1689-1697). All of their children were born in Sandwich. [The Register, Oct 1965, Pg.. 262-266]. Regarding Lt. Matthias 2 Ellis death 30 August 1748 in IGI Page 12078.

Misc. Sources:
Col. Harry H. Ellis, USA, Retired, Dallas, TX.
IGI Massachusetts Pg.. 12078.
History of Ellis - Buckner and Allied Families in America.
Collected by Winnifred Ellis Suman of Lanham, Md. Compiler Janis H. Miller, Washington, D.C. 1973.
N.E.H.G.S. Register, Oct 1965, Pg.. 262-266.
Mrs Frank Ellis, 203 E. Hall, Oberlin, KA. 67749, Jan.1984.

Vital Records of Sandwich, Massachusetts, Volume 1, page 18 is found the following: "Matthias Ellis the son of John Ellis was born the 2d of June 1657".