Given your interest in 1, I think you should read more about the Oneida community, as they were one of the rare cultures which encouraged group marriage. See also https://en.wikipedia.org/wiki/Group_marriage , which specifically calls out Heinlein. There is also the polyamory (see https://en.wikipedia.org/wiki/Polyamory ), which is an active subculture at least in the US, as well as swinging (https://en.wikipedia.org/wiki/Swinging_(sexual_practice) ).

The various literature about traditional poly marriages, which are nearly all polygamous, does not describe a system which aligns well with current ideas of feminism. That said, I know very little about the topic, though I did read 'In my father's house : a memoir of polygamy'.

Some cultures, btw, have legal rights for cohabitation which make it equivalent (or nearly so) to marriage.

There is a body of Heinlein studies, including the Heinlein Society ( http://www.heinleinsociety.org/ ) and Patterson's extensive biographical works. For example, https://web.archive.org/web/20021016160050/http://members.ao... . If you really want to know more about Heinlein-the-person, you might try those. I decided it wasn't worthwhile for me.

Friday, as you point out, is a difficult character to understand. She is an AP, raised in a creche, trained as a spy/agent/courier. Not only was her life was not her own, but her views were even less her own than for most. She may have been trained that her body wasn't her own, that rape is an appropriate means for the field she was in, and taught to expect being raped and how to manage it. And most people saw her as a non-person, including her family in New Zealand. That makes it really hard to disentangle Heinlein-the-person vs. his portrayal of a character.

(The family in NZ, and the quick breakup after they find that she is an AP, is an example of Heinlein depicting a negative to a group marriage. It seems they were more into her for her money than for emotional attachment, and that one or a small number of people in the marriage can force the others to expel a spouse.)

Regarding, "she had to embrace indiginities of human females to be one of them" - this is a topic which comes up when I read discussions about the problems facing trans-women. That's another topic I know little about, beyond following a couple of blogs and watching the ContraPoints videos at https://www.youtube.com/channel/UCNvsIonJdJ5E4EXMa65VYpA .

Regarding "His female characters are almost male in their sexual proclivities." I ask that you re-think that. The idea of female/male proclivities is cultural. I am a male, and don't have the 'proclivities' that Heinlein characterizes. Some males are also asexual, and don't have any proclivities. Your sentence would suggest that neither of us are really male.

I can't explain the incest thing.

"Adult-child sex" is different, though potentially overlapping. (I think Heinlein was referring to incest between consenting adults, so 'child' in the sense of 'the adult's adult child' is closer.) Still, that does occur a few times, like in "The Door Into Summer". Quoting https://en.wikipedia.org/wiki/The_Door_into_Summer#Major_the... :

> The early Heinlein biographer and critic Alexei Panshin, in his 1968 biography Heinlein in Dimension, took note of a controversial theme: "The romantic situation in this story is a very interesting, very odd one: it is nothing less than a mutual sexual interest between an engineer of thirty and a girl of twelve ('adorable' is Heinlein's word for her), that culminates in marriage after some hop-scotching around in time to adjust their ages a bit."[3]:149–150 The novel "worried and bothered" John W. Campbell, who said "Bob can write a better story, with one hand tied behind him, than most people in the field can do with both hands. But Jesus, I wish that son of a gun would take that other hand out of his pocket."

Note also later on that page the description of "Frederica Virginia "Ricky" Heinicke, physically an 11-year-old girl but emotionally almost adult. Like all Heinlein's heroines from this period, she is an intelligent redhead, and clearly modeled on Virginia Heinlein, even having a version of her name and her childhood nickname, Rikki-Tikki-Tavi."

As another example, Tom's great-grandniece in 'Time for the Stars'.

I think to understand Heinlein's female characters, you also need to know more about Virginia Heinlein and their relationship. And be aware that the Heinleins were not always truthful about their accounts of their history. See the note in https://en.wikipedia.org/wiki/Robert_A._Heinlein that 'Grumbles From the Grave' "hews closely to his earlier official bios, omitting the same facts (the first of his three marriages, his early left-wing political activities) and repeating the same fictional anecdotes (the short story contest)."

You write "can I flesh out a male mind with my words if I were a writer?" The classic SF example is James Tiptree, Jr. which was a pseudonym of Alice Sheldon. Quoting https://en.wikipedia.org/wiki/James_Tiptree_Jr. :

> Readers, editors and correspondents were permitted to assume sex, and generally, but not invariably, they assumed "male". There was speculation, based partially on the themes in her stories, that Tiptree might be female. Robert Silverberg wrote "It has been suggested that Tiptree is female, a theory that I find absurd, for there is to me something ineluctably masculine about Tiptree's writing. ... Harlan Ellison had introduced Tiptree's story in the anthology Again, Dangerous Visions with the opinion that "[Kate] Wilhelm is the woman to beat this year, but Tiptree is the man."