I don't know how I feel about Charce with this chapter, so I'll just talk about everything else that's intriguing.
Tricked by Clever Narrative Techniques (again)
At first I was ticked that half of the Chapter 26 flashback was full of lies. But then, I read some Japanese comments about it that pointed out something rather interesting: unlike every other flashback scene in the manga that used gray borders for the panels, the majority of the Ch 26 flashback used black borders.
That is, in that very chapter, Shinohara-sensei had secretly highlighted in plain sight that most of the flashback was a lie, even as Charce was regaling the story. Well played, could it be that Shinohara, in anticipation of this fake flashback, opted to use gray borders instead of black backgrounds as indications of flashbacks?
Still, the gray border panels in that flashback mostly involve Seira, those should be the ones that prove more credible, and higher chance of having actually occurred.
Speculation on Purpose
When Chapter 26 first came out, I commented that the Seira in Charce's photo at the end was awake, had different hair colour and looked older than in his flashback. I was right that he was hiding something.
Given Aries' age, Aries had to have been born at the same time frame as all the other kids in Group B5 (excluding Funicia), and certainly not at the same time as Seira's own birth.
Though Seira is older than Charce, for what purpose was a clone of her created?
"A new younger body" wouldn't make sense, given her age.
"New body to circumvent vegetation" wouldn't make sense either, as based on the flashback this chapter, she was still awake years after Charce and Aries were born.
Aside from possibly "provision of spare organs" like with Funicia's case, I can't think of anything else.
Other questions include:
1. Did Seira herself wanted a clone, or did someone else make that decision for her? 2. How aware was Seira herself of Aries' existence?
3. Why was Aries sent away to be brought up by Ema Spring in the Rosapop Sector (home was listed in Volume 1), and was Seira responsible for the matter?
At the very least, Vixia must've been responsible for Aries' transfer to the Mousanish Sector.
Reasons for Retrieval
This chapter explains a lot of things, among which was Charce's reason for summoning the Sphere on Vilavurs.
So at first, Charce was indeed willing to kill Aries on McPa as well, dismissing the resemblance to his sister figure as coincidence.
But after verifying that she's a clone of Seira on Vilavurs, he changed plans and decided to bring her back to Planet Astra with him.
His reasons could range from any of those listed in the above section, plus possible distaste at bringing any more harm to his sister figure's clone.
One other neat thing that was pointed out on 2ch: so there was a reason why Aries and Charce laughed in the same way in Ship Log 9. They're genetically related.