Because Cadence needs more love…Particularly in the setting.  
Here, Fratello, back from the dead, storms the Crystal Empire with the general intention of wrecking the place and killing his sister. Cadence, resolving to not let the past repeat itself, swears to spare her brother and bring him to his senses the only way she can.  
Realising that, deep down, Fratello still feels and remembers, she takes hold of him and removes the hatred that constricts his heart, taking it into her own body where it will slowly dissipate against the willpower of her own heart.  
Though still heavily pregnant and having no prior experience in battle, Cadence prevails. As Shining Armour and the Crystal Guard approach the crater the siblings stand in and stare in awe, Fratello is finally freed of his cursed armour and stares at her sister with familiar eyes and once more breathes the free air of his homeland.  
Appropriate Music  
“I know your face…Cadence (Hugs her) Cadence…”
 
Fratello’s armour I designed to be a cross between the Predator, Frax from Power Rangers and Lu Bu from Dynasty Warriors.  
His appearance beneath was a bit tricky. I mean, his colour scheme doesn’t resemble Cadence in any meaningful way and I refuse to believe she and Blueblood are related.  
Cadence- Near every shade of pink and purple in her coat and mane.  
Fratello- White coat and blonde mane.  
…  
So to give them some resemblance, I had him resemble Cadence through shape rather than colour, his mane lustrous and curly and his face stream-lined, his eyes with heavy lining and lashes. In a way, he’s a bit androgynous, rather flamboyant, which I feel makes him distinct, in contrast with the hardy Shining Armour.  
I based Shining’s armour of the High Elf armour design in Warhammer. I feel it’s appropriate, alicorn, crystal and heart motifs that match the broken heart sigils on Fratello’s suit.  
The Crystal Guard I based slightly off European knight armour (Since that of the guard of Canterlot resemble Ancient Greek, I tried to make them different) with full plate, decorative visors and crystal inlays and intricate crests.  
Why the Ancient Egyptian-looking pony? Meh, I guess I felt like it.  
A friend? A scholar? An ambassador from the sphinx kingdoms? A sphinx-kin herself?  
You decide.