[Shirazmn]

We are genetic males.

Correct!
Given that I can't find a policy on BreastNexuS that forbids the use to genetic males, BreastNexuM is specifically for genetic males.

I am not talking about one's perceived gender or genitals (TG/TS, in case) but about one's genetic markup.

Then, why do you use these sites? If you are after info about how to grow boobs, knowing that genetically male bodies behave differently from genetically female bodies, you should have little or no interest in reading the other forum. If, instead, you just want to perv on picture of boobs, well...

Some of us, including some admins like Lotus, use both forums to help people regarding the biochemistry of some substances. Most of us, though, including transgender and transsexual people would have no reason to read both.

Again: it's not men/woman. It's XX and XY. If you are intersexed then it makes sense to have an account on both.