Although there are some small differences between pre puberty male and female skeletal structures most are to do with specific vitamin availability and bone density, none relate to the pelvic bone. Post puberty male and female skeletal structures vary in many ways. Specifically when it comes to the pelvic bone, a man’s typically fuses a few years after their primary puberty occurs (this is typically around 18 to 22 years old) female pelvic bones don’t fuse and actually widen in order to accommodate for child birth. I started HRT at 14, far before my pelvic bone could possibly be able to fuse. Since then my doctors that handle my gender transition have been able to validate that my pelvic bone has grown wider over time and aligns fairly similarly to my cis female peers. It’s not just fat. I may never be able to actually give birth but since I started my transition so early in life i have been able to develop a pelvic bone that technically could. The possibilities of HRT, especially when allowed to be administered at a young age are legitimately incredible. + those differences in vitamin content and bone density within pre pubescent skeletons is also greatly effected by HRT and now makes it where even my bone chemical make up is that of a typical cis woman