The boy was shot dead three days earlier by Israeli troops, the youngest of 30 Palestinians killed in an ongoing protest at the border with Israel.
His mother Eman cried as she greeted friends, relatives and neighbors outside the family's home.
Thousands of Palestinians have been staging demonstrations on Gaza Strip's Eastern border with Israel against the decade-long Israeli occupation of Palestinian lands since last week.
The rallies are part of a six-week demonstration that will culminate on May 15, which will mark the 70th anniversary of Israel's establishment -- an event Palestinians refer to as the "Nakba" or "Catastrophe."
"He asked me to buy him a T-Shirt and trousers, and take him for lunch, just me and him," Eman said. "Since the protests began he always came back to me at the end of the day."
At nightfall on Monday, Hussein's uncle set out some candles on a tire lying on the sandy floor of the family's mourning tent. Dozens joined him in singing Happy Birthday.
At least 31 Palestinians were martyred and 2,850 others injured by Israeli gunfire in anti-occupation rallies on border of the Gaza Strip since last week, according to the Palestinian Health Ministry.