On 3 Sep 2020 Brendon Barr wrote on Galicia-18: According to Wikipedia, this person Kuthen’s daughter, Maria married Mstislav, yet Maria’s daughter is also married to Kuthen? I think this needs some actual sources.
Yes, this is hopelessly confused. Kuthen/Köten's wife/wives are unknown (see https://fmg.ac/Projects/MedLands/TURKS.htm#_Toc456164412 as well as https://en.wikipedia.org/wiki/Kuthen).
Moreover, Mstislavna is not a first name - it is a patronym, meaning "daughter of Mstislav".
And the Mstislav Mstislavich of Novgorod who died 1228 is not Köten's father-in-law, but his son-in-law - his wife, named as Maria Kotjanovna here, was actually an unnamed daughter of Köten (see https://fmg.ac/Projects/MedLands/RUSSIA,%20Rurik.htm#MstislavMstislavichdied1228B).
Elizabeth or Erzsebet, the wife of Hungarian king István V, was the daughter of Köten (or at least most likely his daughter); her mother is unknown. There is absolutely nothing to make her a granddaughter of Mstislav Mstislavich of Novgorod (see Wikipedia as well as Cawley, who thinks her father was an unnamed Kuman khan rather than Köten).