Aside from Blackfire Phoenix, who else will gladly be child-free?
I assume you’re talking about the Auraverse so I’ll answer for that! There are a number of characters who I don’t have any children planned for because it’s not relevant to their story, but for some I’m on the fence about whether they might decide to have children later on (Indigo Sprint? Nimble Nimbostraus? Fluttershy’s kids?)
A few characters who I know will definitely not have children ever are as follows:
Brazen Plumage and Enchanting Show, a proud childree queerplatonic pair!
Cheddar Changa, who respects children as much as anyone else but doesn’t want one interfering with their career
Erudite Spell, who also has lofty goals that have no place for a messy little foal (also he can’t get bitches)
Sour Peach, who has the whole world to see and doesn’t want to settle down in one place
Mountain Peak, who sees no need for a spouse and would rather take care of his farm and little niblings
Brackish, for whom child support would be a nightmare
Summer Beauty, who’s having a lot of relationship issues but wouldn’t want to deal with a foal even if she had a chance at having one
Peach Pit…not happily childfree, but she’s accepted her circumstances and is happy to dote on other people’s little ones