Need help naming entire sibset!

I’m writing a dystopian novel set in the future, but I can’t start until I’ve figured out names for all the heroines siblings. They’re all needed for the plot to work but I’m having trouble naming them. The heroine’s name is [name]Phoenix[/name] and she’s fifteen. I will provide her sibling’s descriptions below.

Brother-14

Strong, silent type. Swears a lot to make out he’s cool, but really he’s quite sweet and very clever. He gets depressed a lot.

[name]Sister[/name]- 10

Very sweet and innocent, although becomes less so as the book progresses. Needs a frilly, yet futuristic name.

Twin brothers-8

Hyperactive and always fighting with each other. Can get annoying sometimes. They don’t like to be bossed around.

[name]Sister[/name]-6 months

Doesn’t really have a personality yet.

I was thinking of there being an ‘x’ theme, or mythical creatures or something similar. Only problem is, I can’t think of any names. If you could suggest a few names for each character that would be great.

Brother:
[name]Xavier[/name]
[name]Adrian[/name]
Rivan
Skade

[name]Sister[/name]:
Gidgette
Astana
Kalixta
[name]Selene[/name]
[name]Acantha[/name]

Twins:
Maxxam
[name]Lennox[/name]
[name]Axel[/name]
[name]Jax[/name]
[name]Blade[/name]
[name]Eros[/name]

[name]Sister[/name]:
Xania
Kalixta
Averra
[name]Dianthe[/name]
[name]Xanthia[/name]
[name]Reva[/name]
[name]Xenia[/name]

my fav sib sets - oldest to youngest
X set - [name]Phoenix[/name], [name]Xavier[/name], Kalixta, [name]Axel[/name], [name]Jax[/name] and Xania/[name]Xenia[/name]
Mythological (kinda) set – [name]Phoenix[/name], Rivan, [name]Selene[/name], [name]Cadmus[/name], [name]Dipak[/name], [name]Reva[/name]
Mixed set – [name]Phoenix[/name], Skade, [name]Acantha[/name], [name]Ronan[/name], [name]Tane[/name], Averra