Honestly, I can see this happen more than more than spike and rarity. I didn't think of it until I saw the pictures at the end of the canterlot wedding. Spike kinda has a silly little school boy crush on rarity, sorta something I think he will grow out of. Sweetie belle is also closer to his age.
Also, I really love how you drew Sweetie Belle. I want to hug her ears. owo