While the members of Jonas's family, as with in the all the residents of the community in which The Giver takes place, didn't understand the concept of "love" and certainly didn't love Gabe, they understood that Father was doing a very unusual thing in bringing Gabe home for extra attention and nurturing.Each of them willingly signed the paperwork agreeing to the extra effort that would be required and agreeing that they would not become attached to the newchild.
As the person who worked as a Nurturer, Father was the main caregiver and instructor to the others. They were interested in the novelty of the newchild and were willing to learn what they could do to help care for him.
The newchild, Gabriel, stirred and whimpered, and Father spoke softly to Lily, explaining the feeding procedure as he opened the container that held the formula and equipment.
They played with Gabe, gave him his hippo, and cared for him. Jonas had special abilities that allowed him to soothe Gabe when he was unable to sleep peacefully.