Medics said Israeli aircraft struck four apartments before dawn, including the family's home, killing nine people and wounding at least 15.
Later on Thursday, a separate air strike killed one person and wounded others near Wehda Street in Gaza City, medics said, taking the day's death toll to at least 10.
The Israeli military did not immediately comment.
Reuters footage after the first strike showed a blown-out building with charred and damaged furniture, with debris strewn across the road.
A video circulating on social media, which Reuters could not immediately verify, showed people entering an apartment with blankets to recover bodies.
"We were woken up by the strike at 2.30am. We found pieces of flesh and people were sleeping. They say the war is over but the war is not over," Khalil Batran, a neighbour of the family who were killed, told Reuters.
A girl was the only survivor of the strike on the family home, medics said.
"There is no safety in Gaza ... Every day they fire at us from there and strike us with missiles. It's futile," Batran added.
A ceasefire brokered by US President Donald Trump has failed to halt Israeli attacks and left Israel in control of more than half the enclave after the war began with Palestinian group Hamas' attacks on southern Israel in October 2023.
Indirect talks on a second phase of the deal - including Hamas disarmament and Israeli troop withdrawals - have stalled.
Israel says its strikes aim to thwart imminent attacks and that it allows aid and goods into the Gaza Strip.
About 930 Palestinians have been killed in Israeli strikes since the truce began, according to figures from Gazan health officials.
Hamas rarely provides detail on deaths among its fighters.
Four Israeli soldiers have been killed by militants over the same period, Israel's military has said.
More than 72,000 people in the Gaza Strip have been killed since the war started, most of them civilians, according to Gazan health authorities.
Hamas killed 1200 people and took 251 Israeli and foreign hostages in its October 7, 2023, attacks, Israeli authorities said.
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