The leads in these two stories are completely different. The first story's lead places guilt on the mother by stating, "the mother of the toddler discovered wandering around by himself...has come forward." The second lead does not pin point the focus/blame on the mother, but spreads it out to other family members by stating, "Police say a miscommunication amongst family members led to..."
The main news in the first story gives broad facts about the incident, and it never really describes the miscommunication that took place. All that is stated is that the toddler was found around 4 p.m., he was fully dressed, and that social services were investigating the incident.
The follow-up story provides more details about the incident and pretty much completes the story. For example, the miscommunication was between the boy's grandmother and aunt. One thought the other was watching him and vice versa. The boy ended up outside because he followed his older cousins down the street and got lost. It also reveals that the mother will be in court Monday to potentially regain custody of the toddler.
In conclusion, the follow-up story used the primary story as an outline and filled in the gaps. Without the follow-up, this news story would be a cliff hanger.