There is uncertainly as to Isaac's birth year. Based on the 1742 transcription of Chelmsford records and the main part of the entry in the Chelmsford VRs, the birth year 1661 is used here, however this then shows that Isaac was born only 5 months after his brother Thomas. The Chelmsford VRs show: "Isake Hilldereth," s. Richard and Elizabeth, b. Chelmsford July [20, 1661.T.C.; 1663?]. Davis shows "b. July 20 166."  The records transcribed in 1742 show Isaac's birth on July 20, 1661.
He married Elisabeth Willson of Woburn Nov 12, 1685. [Jul. 24. CT. R.], d. Jan. 28, 1706 at Chelmsford They had the following children:
↑ Title : Town and Land Records, with Births, Marriages, and Deaths, Massachusetts, Town and Vital Records, 1620-1988 [ Ancestry.com. database on-line]. Provo, UT, USA: Ancestry.com Operations, Inc., 2011. Original data: Town and City Clerks of Massachusetts. Massachusetts Vital and Town Records. Provo, UT: Holbrook Research Institute (Jay and Delene Holbrook). Chelmsford records, as transcribed in 1742, Page 4
It may be possible to confirm family relationships with Isaac by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Isaac:
There is uncertainly as to the birth of Isaac. The Chelmsford VRs shows "July [20, 1661.T.C.; 1663?]"; Davis shows "b. July 20 166" and the Chelmsford records as transcribed in 1742 show 1661. Based on the 1742 transcription, I have changed the birth year to 1661. If you disagree, please let me know.