How old do you have to be to petition for your parent to atleast become a u.s citizen?

my father is an illegal immigrant here in the u.s and i want to know how old is it that one is suppoae to be to petition for their parent to be a u.s. citizenHow old do you have to be to petition for your parent to atleast become a u.s citizen?
21How old do you have to be to petition for your parent to atleast become a u.s citizen?
Well, You must be 21 years old to petition your parents. However the trick is when did your parents enter the United States if your parents entered the U.S. years back and someone petitioned then before June 30, 2001 then your parents might qualify to get their Immigration status in order. However if No One has submitted an Application of their behalf then they might have to wait for a new law to pass.
You have to be 21 and he has to leave the USA. It can't be done while he's still here.