In the biblical narrative, Hannah is one of two wives of Elkanah. The other, Peninnah, had given birth to Elkanah's children, but Hannah remained childless. Nevertheless, Elkanah preferred Hannah. According to Lillian Klein, the use of this chiasmus underscores the standing of the women: Hannah is the primary wife, yet Peninnah has succeeded in bearing children. Hannah's status as primary wife and her barrenness recall Sarah and Rebecca in Genesis 17 and Genesis 25 respectively. Klein suggests that Elkanah took Peninnah as a second wife because of Hannah's barrenness.
–Wikipedia