Yes, Phoebe was indeed born in Merthyr Tydfil, but of an English line and the likely line from which Jeremiah would have come was English. It gets complicated! Here I've only included the male line: I know a good deal of the detail on these people -it's just the elusive Jeremiah who is troubling me. I've also omitted children who died young.
It all starts from Thomas Simons 1730-1805 - Gardener of Eton College
Some of his children:
Rev John Simons 1755-1836 - Rector of St Paul's Cray
Henry Simons 1780-1837 Ironmaster, Bowling, Bradford, Yorkshire
Thomas Minchin Simons 1813-1895 Civil Engineer, died Ontario
Edward Minchin Simons 1817-1887, died Ontario
Henry Minchin Simons 1824-1901, merchant in Singapore, died Kensington
Edward Simons 1780-1830, East India Company Army, died Jersey
George Simons 1783- possibly coal merchant in London
John Simons 1788-1871 coal merchant in Camden Town
John Simons 1815-1865 coal merchant St Pancras then charity inspector
John James Henry Money-Simons 1844-1930 Indian Army officer died Switzerland
Kyrle Ernle Symons 1848-1884 Indian Telegraph Dept died India
Herbert Rowland Symons, 1850-1934 varied career, RN and Indian police, died Cornwall
Joseph Gunning Symons FitzSimon 1834-1910, barrister, varying locations including Cornwall, London, Chesham
Thomas Walter Simons, 1836-1899 private income, Clapham
Samuel Simons 1792-1867, private means, Croydon
Daniel Houghton Simons 1798-1822 East India Company army, died St Paul's Cray
Joseph Simons 1761-1802 - salt manufacturer, Chester-le-Street
William Vazie Simons 1792-1843 coal owner, Llanelli
William Vazie Simons 1813-1893 solicitor, Carmarthen and Merthyr Tydfil (Phoebe's father)
Robert Thomas Simons 1827-1855, army surgeon, died Scutari
Thomas Simons 1794-1852 master mariner and merchant, died Texas
Robert Simons 1798-1849 paint manufacturer, died South Shields but married Bristol and also lived Dublin
William Vazie Simons 1823-1897 photographer, miner, chemist, London and Australia
George Neal Simons 1827-1899 master mariner, Shields, London and Kent
Robert William Simons 1828- has disappeared off my radar, I suspect died young
Joseph Simons 1843-1922 - merchant, Barnet and London
Henry Simons 1844 - joiner then farmer, Ontario then Saskatchewan