If your parents are already US Citizen and you are already here in US but in different valid visa, It can take about 1-2 years to get your greencard from the date you file. For that you MUST remain never Married. If you are already married but still want to process your greencard thru your parents, it would take longer than that. In my opinion, about 4-7 years. mine was recently filed so that i still don't know how long it would take but that is wat my immigration attorney told me.. If there are any other experience, that would be appriciated... Thanks..