Meaning of the Sanskrit Word: kumarasya

  kumārasya—of boys like you    SB 4.8.27
  kumārasya—of his newly born son    SB 6.14.33
  kumārasya—of the newly born child    SB 6.14.35
  kumārasya—of the son born of Śakuntalā    SB 9.20.18

Can't find any compound Sanskrit words containing kumarasya.