"Don't be unhappy, mom. Until you find that special somepony, you're always going to have me."
Meet Precious, daughter of Rarity — one of Twilight's greatest creations. After many failed relationships with various stallions and having her little sister grow up and starting a family of her own, Rarity lost her place to pour unconditional love into. To make things worse, she even had to watch her friends move on with their lives while she stayed in one place. Breaking down and slowly losing herself, Twilight came in to her call for help — using her magic to create a perfect little filly for Rarity — a family of her own.
Baaaack to my own personal next gen againnn Upon creation, Precious has Rarity and Twilight's genetics in her. But even so, she is Rarity's and Rarity's only — and she is happy that way. This concept was a suggestion by StarLight-StarFish