Did Moses have an Egyptian Stepbrother? I have seen the Ten Commandments movie from the 1950’s and the Pharaoh has a son which grows up with Moses. This Phaorah dies and his son becomes the King/Phaorah. So Moses approaches this Pharaoh..well his stepbrother! 
The 1990’s version with Ben Kingsley also seemingly depicts The Pharaoh as being his stepbrother too who also hates him. 
Another version with Dougray Scott doesn't make his stepbrother Pharaoh, but he seemingly grows up with him and is a friend?? (Am not 100% positive the character was meant to be a brother)..I didn't like that version very much. This guy later dies in the Red Sea parting. I can't confirm the brotherhood in the last two movies. Because the made up parts can be quite..unusual. 

Is there any evidence Moses had an Egyptian stepbrother in Egypt? Where did this movie tradition start? I honestly thought Moses had an Egyptian stepbrother because of the movies.
The story of Moses is in the Book of Exodus in the Bible and begins in Chapter two. It is a fascinating story and the answer to your question is addressed in:


  Exodus 2:10 KJV  And the child grew, and she brought him unto Pharaoh's daughter, and he became her son. And she called his name Moses: and she said, Because I drew him out of the water.


We do not know whether the eventual Pharaoh you asked about was a natural son of Pharaoh's daughter or not, but being the assumed son of Pharaoh's daughter; Moses would have grown up in the Palace. If the second Pharaoh was the natural son of Pharaoh's daughter, he would have been natural ascendant to the throne.

It is also probable that He and Moses would have been considered as brothers.

Other than those considerations the Bible shows Aaron and Meriam to be the only siblings of Moses.

Hope this helps.