Before 29 Aug 1338 [her father] Edward Montagu 1st Baron Montagu and [her mother] Alice Plantagenet (age 14) were married. She the daughter of Thomas of Brotherton 1st Earl Norfolk (deceased) and Alice Hales Countess Norfolk. She a granddaughter of King Edward "Longshanks" I of England.

After 1352 [her father] Edward Montagu 1st Baron Montagu and Joan Unknown were married.

Before 1361 William Ufford 2nd Earl Suffolk (age 22) and Joan Montagu Countess Suffolk (age 11) were married. It appears he may later have married her sister Elizabeth Montagu Countess Suffolk (age 16) although there is some uncertainty; an example of Married to Two Siblings. And it true, an example of a brother marrying two sisters, and one of those sisters, Elizabeth Montagu Countess Suffolk (age 16), marrying two brothers? He the son of Robert Ufford 1st Earl Suffolk (age 62) and Margaret Norwich Countess Suffolk (age 74). She a great granddaughter of King Edward "Longshanks" I of England.

On 28 Oct 1371 [her son] Robert Ufford and [her daughter-in-law] Eleanor Fitzalan (age 6) were married. She the daughter of Richard Fitzalan 9th Earl Surrey 11th Earl Arundel (age 25) and Elizabeth Bohun Countess Arundel and Surrey (age 21). He the son of William Ufford 2nd Earl Suffolk (age 33) and Joan Montagu Countess Suffolk (age 22). They were half third cousins. He a great x 2 grandson of King Edward "Longshanks" I of England. She a great x 2 granddaughter of King Edward "Longshanks" I of England.

Before 1376 [her husband] William Ufford 2nd Earl Suffolk (age 37) and Isabella Beauchamp Countess Suffolk were married. She by marriage Countess Suffolk. She the daughter of Thomas Beauchamp 11th Earl Warwick (age 62) and Katherine Mortimer Countess Warwick. He the son of Robert Ufford 1st Earl Suffolk and Margaret Norwich Countess Suffolk. She a great x 5 granddaughter of King John "Lackland" of England.

After 1416 [her former husband] William Ufford 2nd Earl Suffolk and [her sister] Elizabeth Montagu Countess Suffolk were married. She by marriage Countess Suffolk. She was previously married to his brother Walter Ufford (age 72); an example of Married to Two Siblings. There is some uncertainty about this marriage since she was the sister of his first wife Joan Montagu Countess Suffolk. He the son of Robert Ufford 1st Earl Suffolk and Margaret Norwich Countess Suffolk. She a great granddaughter of King Edward "Longshanks" I of England.