Is it really true that as a Conditional or Permanent Green Card Holder I cannot apply for an immigrant visa for my parents and sister? Only US citizens can do it?

Yes its true..... you can not file for your parents or siblings until you are a Citizen.... Parents are classed as immidiate relatives and a visa is available to them immidiatley ( well as long as it takes them to process the application).... brothers and sisters there is a wait of many years for a visa to become available to them (depends on where they are coming from)...

Kez

Thank you Kez,
you say that
Parents are classed as immidiate relatives and a visa is available to them immidiatley - you mean after I become a citizen, right?
How can they travel here when I am still a resident? On a tourist visa?
Thanks for all you answers.

Yes you need to be a citizen to apply for your parents.... if your parents want to visit you in the US then they will need a visa to come over... you can check out the requirments for a B1/B2 visa from the embassy website of the country your parents live in...

Kez