Good morning Billy .
Hope all is well on your side of the mountain .
I have owned several jennys , I gave three away just a couple years ago . Also I have owned and worked several mules years ago. I had one mule born here and still have the mom here at the house. ( I bred the mare horse to a jack to create the mule )
I bred twice for a hinny a few years back but failed on both attempts ( jenny bred to stud horse )
The article below explains the reason the hinny is more rare than a mule .
A donkey has 62 chromosomes, whereas a horse has 64. Hinnies, being hybrids of those two species, have 63 chromosomes and are sterile. The cross breeding works best if the lower number of chromosomes come from the male .