You need a separate petition for him.
You should retain an experienced immigration lawyer, whether myself or one of my colleagues, to review all the facts, advise you, and handle the case.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.
Agree, he needs a separate petition as an immediate family member.
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As a green card holder petitioner, your family are not immediate relatives. So you are ok with one petition unless you will naturalize before they enter the us. At that time everyone will need a separate petition.