John b. 1637 and baptized 1640, according to First Congregational Church of New Haven records 
Married (1) 1 Feb 1661/2 Sarah d/o George and Sarah Smith. Sarah was born 1642 New Haven, CT. She died Jul 25 1674 New Haven, CT
The town records give us some information on the early days of John Clark Jr. after the death of his parents. Matthew Gilbert, John Wakeman, Samuell Whitehead, & John Moss, were by the Court, March 5th, 1649, appointed as overseers of the children & estate of John Clarke, deceased. At Court Jan 10, 1658, John's age was stated as 21, so born 1637. After expenses of raising the children for 10 years and some losses, John received 2/5 of the estate as the oldest son. This amounted to 37L, 7s, 10d. For a full transcript see John's or his wife's profile.
Married (2) 28 May 1675 New Haven Mary, daughter of John & Grace Walker, and divorced wife of John Brown. She was baptized Mar 1641 in New Haven, CT
Children with first wife, Sarah Smith Clark, all born in New Haven, Connecticut: 
Sarah, b Dec 24 1662, d 1662
John, b. Jan 23 1663/4, d. 1701, m 1688 Abigail Ambrose
Samuel, b. Aug 20 1666, d. Oct 16 1712, m 1691 Rebecca Brown
Joseph, b. Oct 27 1668, d. 1703, m 1693 Elizabeth Lane
Sarah, b. Oct 24 1671, d after 1747, m John Wilmot, m, Daniel Sperry
Abigail, b Jul 19 1674 (twin), m Samuel Stevens
Mary, b. Jul 19 1674 (twin), d. Sep 22 1675
Children with 2nd wife, Mary Walker Brown Clark: 
Daniel, b. Jun 28 1677, d 1743, m Hannah Beecher
Elizabeth, b. Jan 8 1679, m John Hale
Benjamin, b. Jun 11 1682, d May 13 1712
John died 22 Mar 1719 in the town records  or 23 Mar 1719 ae 87 on his stone at the West Haven Cemetery
Per the New Haven Probate records (on Ancestry), his last will and testament is dated 8 Feb 1716 and he died in 1719.
Profile had birth location as Wethersfield, CT but no sources match to that. Sources state New Haven for birth and baptism.
↑ Find A Grave, database and images (accessed 22 March 2019), memorial page for John Clark (14 Jun 1637–23 Mar 1719), Find A Grave: Memorial #67080846, citing West Haven Green Cemetery, West Haven, New Haven County, Connecticut, USA ; Maintained by Runner Mary (contributor 47186549) .