Short answer: Each of the kid is from a ship that I either think about a lot or used to love. It's very easy to make a character based on something that you're already passionate about!!! (Also thank u 🥹)
Long answer:
I'll use the double meaning of "inspiration" and elaborate on how the parents fuel my creativity hehehe (because I will always find an excuse to yap more)
When it comes to the designs and personalities and stuff I work by the rule that my base is: I take elements that I associate with parents and look for things that are similar or related to it (even if vaguely). But never exactly the same!
For example I associate Duelette with the Sea so Sammy is heavily sea-life themed and even has powers connected to this such as glowing in the dark (like a fluorescent fish). One of the things that they like is pastries so Sammy owns a sweet shop, and so on!
On the other hand their twin sister is more based on other elements like Palette's and Due's love for crafts, trinkets and sweet/cute things, she makes her own plaid skirts and tiny models of places or scenes and keeps a colorful but cozy aesthetic
Lumen Rosa is based on the idea I had of Lotus and Dante both being somewhat elegant and cheeky, those headcanons are a little buried under punk Lotus and "lazy" & messy-mechanic Dante now, so I thought their kid could be that instead! Other thing is that red (Lotus) and green (Dante) reminded me of a rose so I adapted the idea and put it in her theme :^
Vesper is the least "inspired by something specific" one because at first I just wanted her to be yellow and that's all I had for her xD Then I thought "Durik's chaos but concentrated and also put electricity somewhere" boom. But in exchange, she's the only shipkid that I have so far that went through changes from the first ever idea and design! I can say a bit more about it if someone wants but for now I don't want to make this post too long...
When you're making a kid for a ship that has many of them you might try to make something that's less obvious but still fits. So for Nera even their color palette was created like that, I didn't want to just make another red and blue shipkid for afterdeath, so I thought of what could be the mix of those colors. Geno is a smart cookie so she's very analitycal and loves topics related to space, but most of all "death" in space... And psychology because I imagine the Afterdeath household as a very grim one but full of humor (aka coping hahaha... she started by observing their family members), that also makes her a little more upbeat
