how can i apply for my sister to have green card?

[pronto]

Hi. i want to know if i want to apply for green card for my parents and my two sisters,they are unmarried , one is 20 and the other is 15. how should i do? can i apply for all of them together? does my sister wich has 20 years old take a lot of time to receive her visa or she is like the other sister with 15 years old?
thanks

[rayb]

It would be faster for one of the parents to petition both chlidren after the parent arrives in the U.S.

--Ray B

Hi. i want to know if i want to apply for green card for my parents and my two sisters,they are unmarried , one is 20 and the other is 15. how should i do? can i apply for all of them together? does my sister wich has 20 years old take a lot of time to receive her visa or she is like the other sister with 15 years old?
thanks