The children and a woman, whose nationalities were not disclosed, drowned when their boat capsized near the Greek island of Kalymnos, the coastguard said.
Another 11 people were rescued and crews were searching for a missing child, it added, AFP reported.
Nearly 300 people trying to escape conflict and poverty in their home countries have died in the Aegean Sea this year according to the International Organisation for Migration (IOM).
Deadly sinkings occur nearly every day.
On Thursday, a wooden boat carrying dozens of migrants sank near the island of Lesbos after colliding with a Greek coastguard vessel.
Seven people including four children died, and the body of another woman was found on Friday.
Three more people including a young girl and a baby died off Lesbos on Wednesday.
The UN refugee agency UNHCR has reported an increase in the number of migrant boats arriving from Turkey this week.
"The surge in arrivals could be the result of a temporary improvement in the weather, a rush to beat the onset of winter, and a fear that European borders may soon close," UNHCR said Friday.