@Iron Storm  
I think I remember 2 times they were in the background. Once during inspiration manifestation, and once during the starlight Christmas episode…. can’t remember the name on that one. The father has been seen 3 times though. He was fishing in the first babs seed episode. It just bugs me that everyone else’s parents were introduced and then given more time than them, even though they were the 3rd group of parents to be introduced. Twilight and Pinkie had their parents introduced during the cutie mark chronicles.  
Made me sad that we got Dragon Dropped instead.

@Takugenji  
Exactly. I think we saw there father once again as a background character but they were very absent parents. I had hoped the last season would have addressed that issue.

@Iron Storm  
Since they never decided to expand on the family dynamic, I will continue to think that Rarity is closer to Sweetie Belles mother than their own mother actually is. Even though they were introduced in Season 2, they never had another speaking moment, or important event in the show after that.

I can just gear her crying ‘but mommy!’