John Lackland King of England/Jean I Plantagenêt is my 24th great grandfather's wife's 3rd great grandfather.
One branching-pair of my 14th-century, French, 24th great grandparents from which I descend are: Jean de Harcourt V & his 2nd wife Blanche de Ponthieu. Rather than Jean's 1st wife Blanca of Aumale, to whom John Lackland King of England/Jean I Plantagenêt is 3rd great grandfather.