For those of you interested in Perkin, I did some digging at the Moravian Archives in Bethlehem today.
Perkin was born on 17 February 1737. I did not find any information about when he emigrated or when he joined the church, because the Philadelphia Moravian Church records are incomplete before 1776, though I suspect with a bit more work this information could be found. But if as has been noted in print Perkin emigrated in 1774, he would have been 37 or so and could have had children while in England who remained there.
Perkin was a widower in 1778; unclear whether his wife had died in England or whether she accompanied him to America and died here. He was remarried on 10 June 1779 to Willhemina Heuman (pronounced Heyman). They had several children: John (b. 16 March 1781), Maria Henrietta (b. 28 January 1783), Henry Heyman (b. 24 July 1786), and Juliana (b. 15 January 1791, died 2 days later).
I think Joseph Perkin left Philadelphia late in 1793. Willhemina did not join her husband in Virginia until 1794, at which point the children seem to have scattered. John Perkin, who would have been about 13, may have remained in Philadelphia; Maria Henrietta went for schooling to Bethlehem. Not sure where Henry Heyman went. Joseph Perkin himself died in December 1806.
John Perkin, the eldest son, became a Philadelphia physician (and died in 1834). He and his wife had a number of sons--one named, interestingly, Marine Tyler Wickham Perkin, born on 14 July 1820.