Board Thread:Spoilers!/@comment-2153169-20140913181317/@comment-24674051-20140914135724

I wouldn't put any stock in the diffence in hair colors. First of all, I've seen families where natural siblings had different color hair (and various shades of Red for one with various shades of Blonde for the other is not uncommon).

Second, I think Elsa's hair color is not necessarly genetic, but a byproduct of her Ice Magic. Look at what happens with Anna's hair during Frozen. She has the white streak for most of the movie, and it goes completely white after she is struck in the heart, but reverts to completly Auburn after she is saved.

Also, 4x03 was the casting for Prince Hans. There is another prince in 4x07, and based on descriptions, it could be an older brother for Hans, or it could be a different prince altogether (some have even speculated it could be Prince Naveen). I won't speculate who the new prince might be, but there is supposed to be another prince brought in for this episode.