Are you absoluteiy sure that the i797 approval notice is only this year? Anyway if that is the case, then your brother has about 4 years 5 months protection under CSPA. That means he is eligible for a visa as long as his actual age is under 25 years 5 months when his priority date becomes current. Then (assuming you do not come from Mexico or Philippines) the priority date will probably be current sometime in the next year which means he will be eligible for a visa, and he even has quite some wiggle room even if it takes longer than this expectation. (Again - assuming all the dates you have given are correct)