Twenty-nine victims were under the age of 18, reports said, with one official saying 22 were under the age of 14. The death toll rose to 54 on Monday.
The suicide bomber himself was a child aged 12-14, President Recep Tayyip Erdogan has said.
Mr Erdogan has blamed so-called Islamic State (IS) for the attack. Gaziantep, near the Syrian border, is known to contain several IS cells.
On Monday, Turkish officials were awaiting the results of DNA tests as they tried to identify the suicide attacker, the Hurriyet newspaper said.
It added that the type of bomb, which contained scraps of metal, was similar to those used in previous attacks on pro-Kurdish gatherings.
Kurdish fighters, backed by the US-led coalition, have been at the forefront of the fight against IS in Syria.
Prosecutors said a search was also under way for two people believed to have accompanied the suspected attacker to the wedding party but who left before the blast.