The flames erupted from the home around 4 a.m. Tuesday on the 300 block of Margaret Road.
Eva and Ava Brown-Williams, 5, were found in their upstairs bedroom. The family says they died in their sleep.
Their mother, Robyn Brown, was able to jump out of a back window when the fire broke out, which caused her numerous fractures.
She is still in the hospital for her injuries.
READ | Children killed in Upper Darby fire were twin 5-year-old girls, neighbors say
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"The family was already dealing with an unspeakable tragedy," says Carolyn Pugh, the twins' great-aunt.
Just last week, the family lost Denzel Brown to gun violence. He was shot and killed in Strawberry Mansion on March 27.
"This has just been an ordeal, my son lost his wife, and we are burying him tomorrow," said Christina Brown, the twins' grandmother.
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According to the family, Robyn Brown was up past midnight writing her brother's obituary.
Now the family is focused on healing, especially for the twins' two siblings.
"We're just trying to get through this, and I don't know how we're going to do it," said Pugh. "We have to live for the other two and thank God the other two were over my sister's house."
The family has set up a GoFundMe page to help pay for the funerals.
Officials are still investigating the cause of the fire, but they do not believe it was suspicious.