Celestia’s daughter  
Sunnyglow’s mother  
Solstice’s grandmother
 
After Twilight’s ruling of equestria. Celestia’s own daughter is twilight’s student for learning of friendship and all it brings but is also taught the fundamentals of controlling the sun from her mother.
 
Listen I know they introduce luster dawn like smack end of the show. But you can’t shove her at me and expect me to accept she’ll automatically become the next ruler of equestria. Sunset shimmer really tried to steal an element of harmony while being celestias student not all of them will be perfect.  
Anyway Sol becomes queen and her cousin Prince Moonstone rules along side her just as their mothers did all those centuries before. While Twilight raises her own family.