If you are a US citizen you may file the I-130 for him at any time. However, wait times for priority dates will be extremely long. Review the Department of State Visa Bulletin for an overview.
It is currently taking about 10-12 years for a US citizen's sibling to be eligible for an immigrant visa on the basis of a petition filed by the US citizen.
There is not enough information here to make a determination. You did not state if you are a US citizen, where your brother is located, his age, criminal history, etc.
If you are a USC it will depend upon the country your are from. Take a look at the Monthly Visa Bulletin which you can view at travel.state.gov and you will be able to get a sense of the timing.
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