The attack on the district of Maadi killed three people, according to the volunteer group.
Rescuer Ibrahim al-Haj said the airstrikes killed the boy's mother.
Airstrikes pounded rebel-held eastern Aleppo on Thursday, killing more than 20 people and hitting a water pumping station on the third day of a renewed air campaign on the besieged territory, Syrian activists and rescue workers said.
The battle for Syria's second largest city marks a crucial phase of the five-year civil war, in which hundreds of thousands of people have been killed.
The siege and intense bombardment of east Aleppo have created a dire humanitarian crisis, aggravated by frequent air strikes on hospitals and the disruption and pollution of water supplies.
The bombardment hit at least six rebel-held neighbourhoods, said the Syrian Observatory for Human Rights.
At least 65 civilians have been killed in east Aleppo since the start of a regime offensive on Tuesday, said the monitoring group.
The renewed bombardment has shattered a month of relative calm in the devastated east of the divided northern city.
An AFP correspondent in the eastern districts said explosions from barrel bombs dropped by aircraft had been heard since 10:00 am (0800 GMT).
One of the air strikes targeted a civil defence centre in the Bab al-Nayrab neighbourhood with no reported casualties, the correspondent said.
