i want to get three months visa for my mother and sister to come here to hongkong?

If they apply for 3 months Hong Kong visa through China embassy in Manila or consulate in Cebu or Laoag, you need to send them an invitation letter in which the sponsor agrees to provide financial support and accommodation, and one copy of the sponsor's HK ID. You are their sponsor. In fact, you can apply for Hong Kong visa for them through Immigration Department of Hong Kong Government directly.