For a glimpse of intersex characters in my writing, see:
Kenzie Two Foxes, Blair Her Road Goes Both Ways (introduced in "The Place Where the Journey Begins"), and Bobtail (introduced in "Sheltered and True") are two-spirits. Given the small size of her male features and her two-spirit nature, Bobtail may also be intersex. In "TERF Wars," Hassan Saunders (5-alpha reductase deficiency), Marion Rhett (Hermaphrodite superpower), Lennox Oleastro (partial Androgen Insensitivity Syndrome, also a lesbian), and Nicolette/Nicholas le Doux (XX/XY mosaicism) are all intersex. In the same poem, Jayce Olson is MTF while Maren Arntson is a political lesbian. In "Disorientation and Reorientation," Riley Bessonet is intersex with XX chromosomes and ambiguous genitals which appeared vaguely male at birth.
Over in Torn World, the Glifai are essentially all intersex. Historically they were born undifferentiated and then developed as male or female at puberty, with a few remaining neuter. This is somewhat less common now, and more children are born with their sex apparent, but it's still about half-and-half. You can read some Torn World stories about gender.
I'm sure there are more examples, but those are some that are easy to find.