'Sons and daughters' green card process

My grandfather (65 y/o) is a legal citizen of the US, who recently got into an accident and now needs permanent care. My father (42 y/o), who is a citizen of Lithuania, plans to apply for the 'Sons and daughters' permanent green card. If he is approved, he will have to live in the states for 5 years to become a citizen as my grandfather. My question: Can I (22 y/o) apply for the 'Sons and daughters' green card, when my father is not a citizen yet - when he's on the 5 years 'probation' period of becoming a citizen? Or do I have to wait until my father becomes a citizen to get a permission to apply for the visa and enter the country?