What is the meaning of this clause--but it aches even more for him and his entire family when he is 15 years o?

As we headed back into the house, I heard a terrible noise coming from next door. The child of the family living there, also about 15-months-old, went into the street. The boy's father screamed, "Get out of that street, you little brat!" Then in anger he grabbed the boy's arm, gave it a terrible jerk, swung the child into the air at the same time giving him a swat on the bottom, then harshly put the boy down on the lawn. The boy, by now, was crying in pain. You bet, the boy didn't return to the street, nor did he seek out his father for comfort. My heart aches for that boy, but it aches even more for him and his entire family when he is 15 years old!