His subsequent marriage to Euphemia de Ross in 1355 produced two sons and two surviving daughters and provided the basis of a future dispute regarding the line of succession.
On 2 May 1355, Euphemia married Robert Stewart, sole son of Walter Stewart, 6th High Steward of Scotland and Marjorie Bruce. Marjorie was a daughter of Robert I of Scotland and his first wife Isabella of Mar.
It appears that there was an obstacle of affinty to this second marriage, and a papal dispensation by Pope Innocent VI was required for it to be recognized by the Catholic Church. However, there is some doubt about exactly what the affinity between them was. The children of Robert's first marriage to Elizabeth Mure were considered illegitimate by some due to reasons of consanguinity. Both sets of children from each marriage considered themselves rightful heirs to the throne, which constituted considerable future conflict.
Euphemia and Robert were parents to four children:
David Stewart, 1st Earl of Caithness (d. bef. 1389)
Walter Stewart, 1st Earl of Atholl (d. 1437)
Elizabeth Stewart
Egidia Stewart, married 1387 Sir William Douglas of Nithsdale
Robert II succeeded his childless maternal uncle David II of Scotland in 1371. Euphemia became his Queen and served in this position for about fifteen years, until her death in 1386.