I think we should all consider that Rocky grew up genderless on Erid, and spent his whole life feeling strange about it. He was naturally drawn to jobs that are dirty, gross, that have a higher injury rate leaving him with chips and dents in his legs, he didn't want to be pretty or handsome. His carapace got dryer and tougher, and a lot of Eridian's thought it was odd.
Then he met Grace and the first thing Grace did was go 'I wonder if they use pronouns? I don't know how their gender works... I'm just gonna use the same pronouns as me!'
And when Grace explains pronouns and gender Rocky goes "Oh.... Oh I am keeping you." Because Grace -without even realising it- described something in Rocky that he couldn't explain. -Rocky is subsequently ecstatic about using he/him pronouns.
Despite being blasé about it, it only takes a few extra weeks before Grace is wearing skirts and singlet tops more often, and letting the facial hair go wild because who cares? And it kinda... Works, on them. And then Grace freaks out realising they've internally switched to using they/them pronouns personally. It's only Rocky explaining that being gender neutral on Erid is normal, and having a strong sense of gender makes HIM weirder that helps Grace a little.
And then they start having a really supportive, yet utterly befuddled conversation about what the heck is going on with gender between the two of them, and the ultimate conclusion is; do what makes you happy and we can figure the rest out later (or not)!
Anyway T4T Grocky <3 <3 <3