Omer Jarrah

Sayid's brother was portrayed by two actors.

Xavier Raabe-Manupule played him as a child in the 

Season 5 Episode "He's Our You".

Cas Anvar portrayed Omer in the Season 6 episode "Sundown".

I have written to Mr. Anvar, requesting an autograph.

I'll update this post if/when I receive a response.

I haven't been able to locate an address for Xavier Raabe-Manupule