Can I cancel my brother visa f41?

It is a little late in the day to try to cancel your brother’s immigrant visa if it has already been issued. I am not sure that it can be canceled at this stage although you may contact the US Consulate that issued the visa to see whether it is still possible now. Due to the limitations of the Lawyers.com Forums, Alan Lee & Arthur Lee, Esqs.’ (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.