There is no evidence that Antoine de Saint-Exupéry had any children either with his wife, his first fiancée or any of his mistresses. His only blood-heirs are the descendants of his youngest sister.
According to both the Antoine de Saint-Exupéry site representing La Succession Saint Exupéry – d’Agay and the 1994 Stacy Schiff biography Saint-Exupéry, he did not have any children even though he had often expressed a desire to start a family.
Antoine de Saint-Exupéry's marriage (1931 - 1944) to Consuelo Suncín was childless. Earlier, in 1923, he had been engaged to Louise Lévêque de Vilmorin but she had second thoughts; her mother was opposed, Saint-Exupéry was struggling for work (she had refused to be engaged to a pilot as it was too dangerous) and
She was neither the first nor the last woman to remark that he was
impossible to please: “Nothing satisfies Antoine; nothing is perfect;
his demands are not limited by reason. He searches out gray areas and
Source: Stacy Schiff, Saint-Exupéry: a Biography (1994), chapter 6
By the mid 1920s, Saint-Exupéry
More and more often ... expressed a desire to marry. He was sick of
“this perpetually temporary life”; he wanted children, “beaucoup de
petits Antoines.” However, he lamented, he had only met one woman to
whom he had been tempted to make this commitment.
Source: Schiff, chapter 7
That 'one woman' was Louise de Vilmorin.
Saint-Exupéry had a number of affairs, most notably with Hélène (Nelly) de Vogüé, wife of the industrialist Jean de Vogüé, who later wrote a biography of him under pseudonym Pierre Chevrier. There is no evidence of any children from any of these affairs. Given that Saint-Exupéry died without a will and that his estate has been in dispute, it is highly likely that any direct descendants would have come forward (assuming, of course, the individual or individuals concerned were aware of their parentage).
As it is, Saint-Exupéry's only blood heirs are the children (and their children) of his youngest sister, Gabrielle de Saint-Exupéry and her husband, Pierre d'Agay. None of Antoine de Saint-Exupéry's three other siblings had children; his brother died at 15 while his two other sisters were childless.