To qualify as a brother or sister of a U.S. citizen, both he/she and the U.S. citizen must have been children of at least one parent in common. The U.S. citizen petition must be 21 years of age or older. Spouses and children of a F4 beneficiary qualify as derivative beneficiaries. To prove that the petitioner and beneficiary are siblings, the petition must include copies of both their birth certificates, showing there is at least one parent in common.
If the siblings are related only through their father, they will also need to submit the father’s marriage certificate from his marriage to the petitioner’s mother, as well as the one from his marriage to the beneficiary’s mother. If the parents were never married, the siblings will need evidence of legitimation, or proof that a financial or emotional relationship was established with the father at some point before the age of 21.
Because the sibling of a U.S. citizen is at the bottom of the family preference list, the wait is usually very long. Furthermore, because per-country limits apply, applicants from certain counties, namely Mexico, India and the Philippines, typically wait even longer, sometimes up to 25 years.