With the alicorn of magic, and the alicorn of love being the two immortal loves of the mortal Shining Armour, how do they keep a hold of the one they adore?

When the alicorn of love loves her husband with all of her heart, but he is unable to give her a foal, and the alicorn of magic is now powerful enough to cast age-control spells, old age is never a problem.

Quite the opposite, in fact...