Colt but has eyelashes. Hmmm..

Leon is Celestias’ 4-year old Alicorn nephew, possibly a member of Bluebloods’ family tree judging by his obvious appearance.  
Also, Blueblood finally gets a proper full name: Vladimir Blueblood.
 
Head canon:  
Leon is Vladimir Bluebloods’ “disgraced” nephew. Due to Unicorn Elitist Purity found in the Platinum Bloodline, Leon was cast out by his parents to not bring dishonor to House Platinum and sent to Canterlot to live underneath Celestia. Vladimir, the Next-in-Line Head of House Platinum took sympathy on his younger nephew and offered him a home within his manor in Canterlot: having grown up most his life aware of the shame and horrors of their bloodlines’ earliest patriarch Lord Cobalt Platinum. Under Vladimirs’ protection, Leon grew up happy and loved by his uncles and with friends and children in the other Noble Houses.

V Hey guys, Leon and Blueblood are two separate characters

I can’t even tell this pony’s assigned gender

V And lose their wings, apparently.

They are so adorable before they grow up into jerks.