U.S Citizen - Planning to Petition Step Brother (minor), Biological Father & Step-Mother(Unmarried) What is the best approach to do?

You should be able to file for your biological father without difficulty. You will not be able to file for your stepmother as a marriage is required for Immigration to recognize the relationship, and such marriage would have had to be celebrated before you turned the age of 18. With regard to your stepbrother, any such petition that you file would be based upon the stepbrother’s relationship to his biological father. For this, you would have to be able to show that your father either legitimated or took parental concern in his welfare before the child turned 18. Perhaps you could immigrate your father first, and he obtain a divorce when he comes to the US. Then he could possibly marry your stepmother outside of the Philippines, and petition for both her and your stepbrother if the stepbrother is under the age of 21. If over the age of 21, your father would have to put in a separate application for your stepbrother. Please note that I do not profess to know divorce law, and you should consult with an attorney familiar with such before relying on the above advice. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.