Before Discord married Rarity, he had a bit of a relationship with Celestia.  
Together they had a daughter named Ethereal.
 
Some notes about Effie:
 
-While she’s very mature in most circumstances, she has a little Discord chaos in her blood. She’s has a habit of pranking the Palace staff. All harmless pranks that manage to make her chuckle but she rarely takes credit for her pranks.
 
-Effie is a Disney princess. She sings, she talks to animals and has a grand view of how her life should turn out. She wants to meet her Prince Charming and have a fairytale romance. Most Canterlot stallions find her terrifying though so she may have some trouble!
 
-When she’s not by her mother’s side in Canterlot, she likes to visit her father in Ponyville. She’s fairly close to her half-sister and despite being very proper, she loves Chihiro’s unrestrained hijinx…UNLESS Chihiro points her chaotic paws in her directions. She prefers to laugh at the expense of others at the hands of Chihiro.
 

 
 
Last but not least is Aurora Song  
She’s the Queen of Self-confidence and has very little patience for nonsense but loves the drama. If you’ve ever seen Brooklyn Nine-Nine, I based Aurora heavily off of Gina Linetti. In fact, I imagine Aurora’s VA would be Chelsea Peretti.
 
Some notes about Aurora:
 
-She’s EXTREMELY rude but insightful. She doesn’t sugarcoat things and will just tell you what she thinks of everything. Unfortunately, if she can hear a conversation even if it doesn’t involve her, she will get involved.
 
Pony 1: And so I dumped Sprinter Fling! He was so weak and I don’t know why I put up with him!  
Aurora: Maybe because he did the heavy lifting to make up for your shit personality.  
Pony: HOW RUDE!  
Aurora: [Looks her up and down] Now that I look at you, I think the only thing you’d bring to the relationship is noise. Purple doesn’t suit you.
 
-She works at Rarity’s old Ponyville Boutique with her manager Yona. I think if she didn’t have such a keen eye for fashion Yona would have fired her ass with literal fire. Aurora is a handful and Yona is close to done with her ‘tude.
 
-Aurora’s moms are Silverstream and Sweetie Belle. Both travel a lot to help blank flanks in need so she basically lives with her grandparents or Rarity most of the time. This mildly upsets her but on the other hand, she finds her moms overbearing when they are around. She loves them both dearly and she’s the least critical of them.
 
-Aurora is the only creature that can comment on Rarity’s appearance without the aforementioned diva flipping her shit. Aurora has an amazing eye for beauty and Rarity actually comes to her a lot for clothing advice. Aurora is not a professional but she knows what works.