Debbie Boyd, whose sister Nancy Worrell was the one adult killed in the fire, said her sister wouldn't have left the burning home with any of the children inside.
"My heart is heavy," Boyd tearfully told reporters while standing outside the blackened brick home. "My heart is hurting."
Baltimore Mayor Stephanie Rawlings-Blake visited with the family on Thursday afternoon and called the fire "a tragedy all around."
Two firefighters were also injured and were in stable condition.
Associated Press writers Karen Mahabir and Jessica Gresko in Washington contributed to this report.