Who were the wives of Manasseh and Ephraim? What were their backgrounds? Who were their parents? Did they have concubines? If so who were they?
According to some readings of I Chronicles 7:14, Menasheh had an Aramean concubine:
The sons of Manasseh: Asriel, whom his wife bore--his concubine the Aramitess bore Machir the father of Gilead; (Mechon-Mamre translation)
See, however, Malbim (ad loc) who offers an alternative translation.