He was the only boy in a family with eight children.
He was the only boy in a family of five siblings.
And, yes, that was the only boy to go to her room today.
He was the only boy on the island whose hair never seemed to grow.
He was the oldest of three children and the only boy.
He is the only boy in his family and has two sisters.
He was the only boy at Queen's who had his own car.
He is the third of five children, and the only boy.
Richard was the second of three children and the only boy.
He was the only boy who didn't have a water pistol.