People out here coming up with all these headcanons where Grace is Rocky and Adrien's third mate, or like an uncle to their kids, or, like, their pet?
But Rocky is almost 300 years old. Adrien is probably similar. He talks to Grace the same way one would a toddler because the Eridian language is so impossible as far as their cross-species limitations and he has to dumb it down. He bends his own mathematics and units of measurement to Grace's because he knows Grace can't keep up.
But Grace is also super smart and far more intelligent than any animal, so he's definitely not a pet. He teaches Rocky plenty of new things too, after all.
Grace is also only, like, 40 when they arrive at Erid. Rocky was already stranded at Tau Ceti when Grace was born. Rocky is older than the country Grace comes from. Rocky was already on the Petrova Line mission the day Grace came out the womb.
Rocky and Adrien don't marry Grace or whatever, or make him an uncle to their kids, or their pet.
Rocky and Adrien ADOPT Grace because he is baby. Baby human, so lost, fragile, talk like toddler. Genius toddler, but still, baby. Teach other kids for enrichment, yes, yes.
And yeah, Rocky is Grace's best friend, but he's also his protector once they get to Erid. He's the one that has to advocate for him, support him, speak on his behalf, figure out what's best for him, mediate. Rocky is 250 years older than Grace. Grace is baby that claims Rocky is his best friend. Of course Rocky is his best friend as well--he's the older, wiser guardian now tasked with protecting this squishy, leaky, blob pebble. It's the same way a child looks at their guardian and claims them as their best friend, except Grace will never age out of it. Grace means so much to Rocky--he's the poor baby alien genius he found with no family floating around in space.
People comment on Rocky being sassy by bossing Grace around or having attitude because he refuses to teach Grace Eridian swear words (this is implied to have happened when Rocky is admonishing Grace for leaving the taumoeba out at room temperature, refusing to translate one of the words he was using). But people rarely mention how Rocky scolds Grace for bad behavior, and even occasionally tempers his reactions when Grace is trying his patience.
But, going even further, Rocky will do the very parental thing and, when Grace screws up and is clearly feeling really bad about it, will comfort him by assuring him it wasn't that bad. Example, when Rocky is gravely injured saving Grace's life, Grace makes a HUGE mistake in trying to help that nearly kills Rocky. And when Rocky tells him this, he explains the situation quite gravely, but also, as soon as Grace shows extreme remorse and guilt, assures Grace that, actually, given how long Rocky had been sleeping when Grace made this mistake, it was probably fine, what Grace did. In fact, maybe it did even help a little.
This exchange was curious to me at first, because Grace--from our perspective--is an adult, and it seemed very odd to swing from "you nearly killed me" to "actually it was probably fine, don't feel bad, it might have even helped" within moments given that Grace should be able to handle both the consequences of his actions as well as what it could teach him about Eridian biology. Instead, Rocky goes on to placate him because it's clear Grace is devastated that he fucked up so badly. Maybe there is truth to what Rocky said and maybe what Grace did WAS ultimately helpful, BUT I always interpreted this as Rocky realizing that his poor alien child did his best to help him in a horrible, scary situation and unintentionally made it worse and now he's spiraling and upset and no, no, no, we can't have that, "it's okay, it's okay, it helped, you helped, don't be upset, everything is fine, I'll be fine, shh, shh, shh, I'm alive and I'll get better now, don't be sad."
So, if you take their ages into account, of COURSE Rocky is going to act like he's the one in charge, telling Grace what to do. Of COURSE Rocky's not going to teach Grace bad manners like swearing. No matter Rocky's ability to acknowledge that Grace is extremely mature, intelligent, and capable, no matter how often he does relate to Grace as an equal, and no matter how dependent Rocky is upon him for the mission--
Grace is still practically a child from Rocky's perspective. Maybe a teenager, and so Rocky can get away with ribbing on him and chastising him more harshly. But still, very, very young.
There are even points in the book where the way Rocky talks to Grace, he sounds like a parent or much older sibling. Some of this is likely attributed to their language barrier, but then, that's not the only way to interpret his tone.
Additionally, Grace's adoration, trust, and starry-eyed admiration for Rocky is also very "this person is much older than me and I trust them implicitly with my life because we're friends but also he's the adult in this situation. He's so capable and an engineering genius so of course I would let him do open heart surgery on me and trust without question that everything he creates and designs is flawless, because he is PARENT (hundreds of years older) and I am "CHILD" and the trust is unshakable." Even when Grace starts to doubt Rocky's engineering (which is basically unfathomable to him--again, VERY parent-coded and not exactly best friend coded, because most of us with best friends have no issues acknowledging that they're probably not the end-all be-all of answers and skills), it ends up that the mistake was actually Grace's and Rocky's flawless engineering remains intact.
Rocky and Adrien are Grace's new parents, is what I'm getting at here.
And when Rocky and Adrien have their first biological child, they refer to Grace as Older Sibling Grace.
Fight me.
EXTRA: And also, those AUs going around where Grace gets an Eridian body when his human body dies? Huge miss that not more people are making him a pebble/teenager. When he does die, he's still VERY YOUNG by eridian standards, and so the body he gets could reflect that. He could be one of Rocky and Adrien's children, as even if he'd lived to be 100 (which is unlikely given all he's been through and the gravity he has to deal with on Erid), he's still only the equivalent of 10 to 15 to 20 years old (20 might be pushing it). Granted, we don't know the actual rate at which Eridians age--maybe they age quickly and become adults by age 30, who knows, but still, huge miss. Say Grace lives to be 100 (he won't), by that time, Rocky will be around 350. Big parent/much old sibling energy there. And yeah, Grace is an adult by human standards, so you could ratio out their ages, but, like, that's no fun.
