If you are a female,
All elder brothers are 오빠, the eldest brother is 큰/첫째 오빠, the next brother is 둘째 오빠, 세째 오빠, 네째 오빠.... etc.
The last elder brother is 막내 오빠
My older brother is a lawyer and my middle brother is a doctor
큰 오빠는 변호사고 둘째 오빠는 의사예요.
If you are a male,
All elder brothers are 형, the eldest brother is 큰/첫째 형, the next brother is 둘째 형, 세째 형, 네째 형.... etc.
The last elder brother is 막내 형
My older brother is a lawyer and my middle brother is a doctor
큰 형은 변호사고 둘째 형은 의사예요.