Here are how the Sirens are in Equestria again.  
I’m afraid that these design are kind of an eye strain because of all the colours, so i’m sorry. I got really inspired by Splatoon’s designs and Visual Kei/Harajuku fashion that i couldn’t stop myself
 
The children of the Sirens, almost as vain as their mothers. (from top to bottom)
 
??? (i still don’t have a name for him, so feel free to suggest one if you would like!): The result of an one night stand between Adagio Dazzle and Stygian/Pony of Shadows (stygian doesn’t know). His siren form has tentacles like those of an octopus/kraken.
 
Rhapsody Allegrezza:Daughter of Adagio Dazzle, the pop star Countess Coloratura and their manager Svengallop, a true diva. Her siren form resembles a leafy seadragon.
 
Vaporwave Koi (left): Son of Sonata Dusk and the dj Vinyl Scratch, obsessed with his appearance. His siren form resembles a mix between a koi fish and a betta fish.
 
Crescendo Profundo (right): Son of Aria Blaze and the bass player Octavia Melody, perfectionist. His siren form resembles a lantern fish.