She is married to Thomas Grey.
They got married in the year 1381 at Heton, Northumberland, England, United Kingdom.
Child(ren):
Said to be daughter of John de Mowbray and Elizabeth de Segrave. 4 sons & 1 daughter
There are at least two sources which identity Thomas Gray's wife, Joan, as the daughter of John de Mowbray. The first source is the Visitation of the North taken c. 1480-1500 in which Joan is called "Ionetta filia Johannes Moubray." [Reference: Surtees Soc., 144 (1930): 53-54]. The visitation is one of the earliest visitations on record and one of the best in my opinion.
The second source is the monumental inscription of Joan (Mowbray) Gray's son, Henry Gray, which reads as follows:
"Here lyeth Syr Henry Grey, the sonne of Syre Thomas Grey, and Jone, hys wyf, that was systere to the Duke of Norfolk, that dyed at Venis." [Reference: Scott, Memorials of the Family of Scott (1876), p. 126
footnote p].
The Duke of Norfolk who died in Venice was Thomas Mowbray, Duke of Norfolk, who died there of pestilence in 1399. He was the son of John de Mowbray, 4th Lord Mowbray, and his wife, Elizabeth de Segrave.
I trust that answers your question.
Best always, Douglas Richardson, Salt Lake City, Utah
Jane de Mowbray; m. Sir Thomas Gray of Wark.
Joan de Mowbray; m. Sir Thomas Grey of Heaton, d. c 30 Nov 1400.