When going through Infinity's terminals, I noticed that the Pfhor's bureaucratic terminals studiously avoid using pronouns anywhere. As a result, it's almost impossible to ascertain the gender of any specific Pfhor (assuming that it is even possible to analogise the Pfhor's genders to ours). I was able to find references to the genders of the following Pfhor:
• Tfear: male (probably first mentioned by Durandal, but I don't really remember for sure)
• Hlford: male (mentioned by Durandal in "What About Bob?")
• R'chzne: male (mentioned by Tycho several times)
• Great Mother crouched behind the Throne: presumably female (mentioned by Tfear in "Aie Mak Sicur")
• Unnamed Pfhor in "Thing What Kicks...": male, according to Durandal
• Hindmost Creche (which is probably a metonymy, since a creche is a nursery): female, mentioned by Tfear in "Slimy Things". Notably, he capitalises the pronoun "Her" in a way that suggests She is a figure of some religious reverence. My headcanon is that "Hindmost Creche" is a metonymy for the Great Mother, although this is not officially confirmed anywhere. (Interestingly, Tfear also uses the phrase "dried creche" in the aforementioned "Aie Mak Sicur" terminal.)
That's all I was able to locate; although several other Pfhor are named and even, in some cases, given individual personalities, their genders are a complete mystery. (It's possible that I missed one or two, of course.) The only reference I could find to the gender of any Pfhor in any "bureaucratic" terminal is this forgery by Tycho, and I suspect this was done deliberately as a sign that it is a forgery: https://www.lhowon.org/terminals/marathon-infinity/1_s2u_p1.png
Of course, characters in Marathon having no defined gender is hardly restricted to the Pfhor. Pthia's gender is never once mentioned in any of the three games, and although some players may assume that all the Bobs are male, there's really nothing explicitly confirming this anywhere.
Anyhow, a number of people in the Discord appear to have believed the Hindmost Creche was a group, which is not correct. As a result, I felt compelled to document the known genders of Pfhor, only to discover that the list is extremely short. It may be of interest to others, so here it is.