Informal:
* Братик, иди сюда! (Brat-ik, idi syuda!) - This is the most casual way to say it, using the diminutive form of "brother" and a direct imperative.
* Малыш, иди сюда! (Maly-sh, idi syuda!) - This translates to "Little one, come here!" and is even more informal.
* Иди сюда, братан! (Idi syuda, bratan!) - This is another informal option, using the slang term "bratan" for brother.
Formal:
* Младший брат, подойдите сюда! (Mladshiy brat, podoydite syuda!) - This is the most formal way to say it, using the word for "younger brother" and the polite form of "come here".
Other options:
* Приходи сюда, братик! (Prikhody syuda, brat-ik!) - "Come here, little brother!"
* Подойди ко мне, братик! (Podydi ko mne, brat-ik!) - "Come to me, little brother!"
The best way to say it depends on your relationship with your brother and the situation.