Editing Lord Kelvin (section)

=== Family ===
[[File:Thomson family lineage.png|thumb|The Thomson family tree: [[James Thomson (mathematician)]], [[James Thomson (engineer)]], and William Thomson, were all professors at the [[University of Glasgow]], the latter two through their association with [[William Rankine]], another Glasgow professor, who worked to form one of the founding schools of [[thermodynamics]].]]

Thomson's father, [[James Thomson (mathematician)|James Thomson]], was a teacher of mathematics and engineering at the [[Royal Belfast Academical Institution]] and the son of an [[Ulster Scots people|Ulster Scots]] farmer. James Thomson married Margaret Gardner in 1817 and, of their children, four boys and two girls survived infancy. Margaret Thomson died in 1830 when William was six years old.<ref>{{cite web |url=http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thomson_James.html |title=Biography of William Thomson's father |publisher=Groups.dcs.st-and.ac.uk |access-date=29 October 2011 |archive-date=2 May 2019 |archive-url=https://web.archive.org/web/20190502040147/http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thomson_James.html |url-status=dead }}</ref>

William and his elder brother [[James Thomson (engineer)|James]] were tutored at home by their father while the younger boys were tutored by their elder sisters. James was intended to benefit from the major share of his father's encouragement, affection and financial support and was prepared for a career in engineering.

In 1832, his father was appointed professor of mathematics at [[Glasgow]], and the family moved there in October 1833. The Thomson children were introduced to a broader cosmopolitan experience than their father's rural upbringing, spending mid-1839 in London, and the boys were tutored in French in Paris. Much of Thomson's life during the mid-1840s was spent in [[German Confederation|Germany]] and the [[Netherlands]]. Language study was given a high priority.

His sister, Anna Thomson, was the mother of physicist [[James Thomson Bottomley]] FRSE.<ref>{{Cite web |url=http://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf |title=Former Fellows of The Royal Society of Edinburgh, 1783–2002 |access-date=30 April 2015 |archive-date=19 September 2015 |archive-url=https://web.archive.org/web/20150919152306/https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf |url-status=dead }}</ref>