Scribe
Legend
D&D has canonically allowed reptilian (dragons), undead (vampires) fey (nymphs, satyrs, and hags) and all manner of planar (fiends, angels and genies) to produce viable offspring. Biological compatibility in D&D is more a guideline than an actual rule...
Yeah, I default to 'A God made it happen.' Any other path is both madness, and slightly (or majorly) gross.