My wife is now a US citizen. She is looking to apply for her parents to come over. They have children, 1 is 36, 1 is 24, 1 is 21, 1 is 18 the last is 16. She would like to apply for her parents and her 16 year old sister at the same time. When the parents get here in 2 - 3 years, have them apply for the others once her parents get a job. I told my wife it may be possible for the 18 year old, but the others would be a wait of 8 to 10 years. Although I have read elsewhere that it's between 3 to 5. What would be a good approximate for this? Thank you.