Is she referring to the likelihood that one parent was human and the other a horse? If so, isn’t this an odd question for on magical creature to ask another? Surely she’s seen countless centaurs before.
Kind of weird, by the way, that this comic with a magical being shooting arrows appeared a few days before St. Valentine’s Dy yet apparently has nothing to do with it.
Comics I Don't Understand 
Evidently somebody didn’t see “Fantasia”.
She hasn’t seen a lot of centaurs before because she’s a recent immigrant from Ireland. The real joke, of course, is that centaurs are supposed to be great archers and he’s about to have the arrow fall off his bowstring.
Each of his parents was a centaur.
They met on Cupid.com.
I like to think that every horse-human union is a unique occurrence
His parents met at a speed-dating event at the Civic Centaur.
I’m not sure it’s proper to laugh at this offspring of a mixed marriage.
A rodeo seems to be an obvious answer.
Paraphrasing Larsen: “You have to understand, in the 60’s we took a lot of drugs.”
I’m guessing his mother was a perfectly nice human, but his father was a real horse’s a**.
Sign in my gyn’s office: “This Valentine’s Day, be sure that the arrow that sets you aquiver comes wrapped.” Courtesy of Trojan.
My spellchecker didn’t like ‘aquiver’. Such limited vocabulary.
In Xanth, centaurs exist but are VERY shy about discussing sex with non-centaurs. Like Ed Meese, only also good with archery.
Nobody’s going to make a joke about “dangers of inviting an equine friend over for some wild oats, and then horsing around” joke? I’m surprised.