I think Oceanus really does care about her fellow shadow dragons! All this info comes from Dragon Ball Heroes - Victory Mission, which I don't think is canon but there's no reason to assume the personalities aren't accurate! Especially since it was written by Toyatarou, the current writer of Dragon Ball Super.
Exhibit A:
When Haze is struggling, Oceanus intervenes and gives him a massive power boost, presumably using the energy meant for reviving Syn Shenron. She really didn't have any reason to do this, that energy is definitely more valuable going towards the revival of the strongest Shadow Dragon than being used to give the weakest a boost! She plays it off as "oh wow you're struggling guess I have to help you out..." but she easily could have left him for dead!
He might look a bit shocked, or even scared when she gives him the power boost, but this definitely isn't to his detriment! He enjoys the new power so much he gets carried away and starts claiming he'll "destroy the universe!"
Exhibit B:
As the other Shadow Dragons are hunted down by Genome and his SSJ4 Broly, Oceanus and Rage are visibly shaken by it! This is the easiest point to explain away, as it would be fairly reasonable to say that the two are more shaken by the threat to their own lives than anything else...
But the line "at this rate, before the one-star dragon revives, our bodies will..." does kinda imply that she's worried about all of them and not just herself. After all if all she cared about was herself she could abandon the idea of reviving Syn and leave him and rage to their fates!
Exhibit C:
THIS is the part that convinced me she really does care about the others! Broly goes for Rage Shenron at full force, and Oceanus is terrified. Reasonable reaction! Broly is a scary dude!
But does she try to flee? Use Rage as a distraction and get out of there? No. Her first reaction is to jump in there and help him! This demon has killed several of the strongest Shadow Dragons with ease, defeating Eis Shenron in a single blow, and Oceanus is still ready to jump in and help Rage Shenron fight him. If Genome hadn't stopped her. And she looks so angry at him for that.
At this point she's bargaining for her life. She can't save Rage, all the others are dead, and she doesn't stand a chance against these monsters. So what does she bet everything on? Syn Shenron. If she can just revive him, that's her best chance at surviving. Even in this desperate move, her focus is on another Shadow Dragon.
and finally...
Exhibit D:
Even as she strikes a deal with Genome to revive Syn, Rage is defeated by Broly. And even being confident that this will work in her favour, she can't help but look disgusted at him holding Rage's Dragon Ball.
Just one of these wouldn't make a great argument, but you put all of these moments together and it becomes hard to deny... You love your brothers, don't you Oceanus? Even if you'd likely never admit it!
The manga was cancelled shortly after this, so it's hard to say how things would have gone, but I doubt it would've ended well for my girl... Syn almost certainly doesn't hold any familial love in his heart for his fellow dragons, and almost certainly would've wanted her Dragon Ball to become Omega Shenron. The bastard's predictable like that. Prehaps she would've at least gotten some solace in him beating the snot out of Genome though!
Do any of the other dragons care for their siblings? There's no way to really tell, despite all this showing of Oceanus caring for the others this manga doesn't have the other dragons interacting with each other outside of this!
And the only interactions in their actual source material, GT, are between Nouva and Eis, and Nouva and Omega! Nouva and Eis bicker and argue, and Nouva seems to care more about getting his honourable fight with his man-crush Goku than anything, sabotaging Eis and causing him to lose to Goku! Doesn't seem very brotherly to me, but to be fair he does try to get Goku to spare Eis, even though that turned out to be a trick by the Three-Star Dragon. And of course, Syn is a dick and kills Nouva for his Dragon Ball.
So not much evidence of them caring about each other outside of Oceanus Shenron! A surprising little detail that makes her all the more endearing to me 💙
