this is Melody, her cutie mark symbolizes she's talented with music (or singing or she can make musical scores and she has a brother named Royal Riff)

Royal riff on a taxi by pikamander2-d577dt3

Royal Riff's expression when he see's his sister again

Melody and Royal Riff having the same cutie mark

They both noticed they have talents for music related things, and some how ended up with the same cutie mark, so they decided to work together (i didn't really know Royal Riff had this cutie mark, i was starting out on making these.) but as there fame grew so did there ego's for making music.. and they realized that one of them must be the most talented...  

As Melody came to know that she needed her brother's share of music just as much as she needed her fame... so she set out to look for him, but the ponies in her town didn't know where he was.... and.... she gave up... and then decided she can go on the road with her skill and find him from that way. 

(now that i realized it's fun to gender bend these bronies, i am now doing that.. but i like this idea... yep, i made this up just now.... i can be creative when typing). ;)