[en] A Monte-Carlo simulation has been done which includes a jet production process based on QCD theory in order to see its effect on gamma-ray families. In the present paper, jets with Pt > 4 GeV/c are considered. Many of the effects the hard scattering gives on the family are similar to those brought about by heavy primary cosmic-rays. In many of observed quantities, however, the effect is statistically insignificant. The QCD jet can contribute to increase the number of clusters in a family, whilist it is not a main source for generating double core families, though it has potential of giving double core families of the largest separation. It is also concluded that the increase of the transverse momentum with energy in the fragmentation region should be very weak. This is discussed in connection with jet production with Pt < 4 GeV/c and correlation of Pt and multiplicity. (author)