So to explain Royalverse, pretty much Luna, Celestia, Twilight and Cadence are together in a poly-amorous couple, trying to create children to replace the elements of harmony. THEY ARE FAILING HORRIBLY.
Flurry Heart lives with her father, Shining Armor, who disliked the idea from the beginning. He was remarried to Rarity, they had one son and got divorced shortly after, and now he is trying to date any other pony intrested
Atlas resents the princesses for ruining his mother, he plans to overthrow them in some way (fails badly)
Prince Titan has a son, with one of Sunset and Sci-Twi's daughters, she ran away from her parents shortly after due to the shame.