Rainbowdash's far away cousins:

Spectrum (Spectra/Spec)
she can shine her rainbow colours by flying near the sun, she will make a rainbow when she does that. (even though she hasn't found out yet)
Cutiemark: has no cutiemark yet
Has a brother: Neon.
She has a crush on Fizzletwist and is verry insecure about her cutiemark, she knows that every member in her family has the ability to shine out beautifull colours .. she tries but just don't know how to.

Neon (Neo)
his neon coloured mane glow in the dark and he knows how to Rave!
Cutiemark: Volume balks in neon colours
He is Spectrum's big brother and verry possesive of her
He goes to the most famous raver parties in Equestria and tries to get all the mares.
He hates Fizzle for stealing his sister.