Complex sentence: Sirius as a teenager made a brief appearance in "Order of the Phoenix" (played by James Walters), and is also slated to appear in "Deathly Hallows", to be portrayed by Rohan Gotobed.
Split into simpler sentences: Sirius as a teenager made a brief appearance in "Order of the Phoenix" (played by James Walters). Young Sirius is also slated to appear in "Deathly Hallows", to be portrayed by Rohan Gotobed.