Why is it that jason doesn't acknowledge his biological sister and her 6 kids? such a humanitarian that he is!

biologically jason and myself share the same mother yet he does not acknowledge me. He is well aware of my existance as well as that of my 6 children. he does so much for single moms yet won't acknowledge his own nieces and nephews. our mother knows exactly where i live but fails to acknowledge my existance and i just think its a shame.