Anderson, the spokeswoman for the Cleveland FBI office, said investigators will question the three women found Monday in the hope that they know something about Summers' disappearance.
Of the three brothers arrested, Ariel Castro was the only one to live at the home where the three women were apparently held, police said. The others lived elsewhere in the city.
Their uncle, Julio Castro, told CNN's "Anderson Cooper 360" on Monday that his family had grown up in the same west Cleveland neighborhood and knew the Georgina DeJesus family.
Julio Castro told CNN's Martin Savidge on Tuesday that family members were "surprised" over the developments.
"Shame on you," Julio Castro said, when asked what he would say to his nephews.