Margaret of Scotland, Dowager Countess of Richmond (1144/45-1201) was apparently married at least three times. There is no argument about her first two marriages: 1) Conan IV, Duke of Brittany (through whom she obtained her title) and 2) Henry de Bohun, 1st Earl of Hereford, through whom she received her alternate title of Countess of Hereford.
She was widowed again c. 1180/81, still young enough to be fertile and with several living children to prove it.
Either she, or an otherwise unrecorded daughter of the same name, married conde don Pedro Manrique de Lara Vicomte de Narbonne shortly before 1183. Reasons for thinking it was a daughter instead of her include the age discrepancy between Margaret and don Pedro (he was some ten years younger), and the plain fact that don Pedro married a third time before 1200 (Mafalda, widow of Pedro Rodríguez de Guzmán), while Margaret of Scotland was still alive (she died in 1201). http://fmg.ac/Projects/MedLands/SPANISH%20NOBILITY%20LATER%20MEDIEV...
It has also been stated that her third husband was William FitzPatrick alias de Hertburn, alias de Washington, of Greenlaw, Westmoreland, and that they had at least one son, possibly two plus a daughter. http://fmg.ac/Projects/MedLands/SCOTLAND.htm#Margaretdied1201 (This is the William de Hertburn referred to in the Boldon Buke, as acquiring Wessington in exchange for his Hertburn lands in 1183. https://books.google.com/books?id=1-g3AAAAYAAJ&q=wessyngton#v=o... ) (Wikipedia states this marriage as fact, but you all know Wikipedia....)