Since you seem less sure about your boys' names, here is a list of some boys' names. I tried to avoid repeats, but I didn't really check over it too thoroughly...so there are probably at least a few in there. Sorry!
Some unusual and manly (in my opinion, at least) Germanic names:
Korbinian (there's a diminutive listed that's pronounced KUUR-bəl; part of me wants to suggest Kobol - like, the ancestral homeworld from Battlestar Galactica - as a nickname...because I am a nerd. While I'm talking about BSG, I guess, I also think Agathon is pretty BA)
Thorben / Torben
Rayner / Reiner / Rainier / etc.
Etzel (a form of Attila, apparently)
Madoc / Cadoc
Faolan / Phelan
Sylvan / Sylvain
Merit / Meritt
Barnaby / Barnabas
Octavius / Octavian
Bohdan / Bogdan
Spyros / Spyro / Spyridon / etc.
Orland / Orlando
I do love Inara. Nova and Briony are also some of my favs for a girl. Boys can be a lot harder... I think my boys will end up with overly normal names, just due to the husband vetoing. :P I do like Rourke, but I'm not sure how it'd go with Lucian...
Both Lucian and Inara mean "light"... So why not go for a name that means "light" for a boy?
Tane (Maori God of Light)
Raiden (Japanese God of thunder and lightening)
I also like Caelum, Latin for "sky".
Vladimir, Vladric, Dragomir, and Balthazar may be too much for a little boy to live with. Actually, that's probably a really bad idea. I love Magnus, Roarke and Ronan, but right when I saw Lucian I thought Gideon, Kieran, Donovan, or Phineas would go really well! Alastair is also a form of Alexander, and would be kind of cool for a middle name to match Lucian's. Lucian Alexander is strong and powerful without being over the top, and I think that's an important trait to keep when naming his sibling.
Inara, Nuada, Nuala, Artemis and Athena (though I LOVE the last two to bits) are names that also could cause some troubles for your little girl. Thisbe, Aurora, Gwendolyn, Althea, Aurielle, and Zelda are very cute. I think Gwendolyn looks the best with Lucian, but Aurora is really cool too. Phoebe, Helenore, Nera, Luna, Livana, Keira are all names that would work well with Lucian.
I think your style is... well, how can I say it? Dark Souls-y.
Boys - Vladimir, Dragomir, Balthazar
Girls - Inara, Nuada, Nuala, Artemis, Athena
Boys - Gideon, Kieran, Donovan, Phineas, Alastair (for middle)
Girls - Gwendolyn, Aurora, Althea, Aurielle, Zelda, Phoebe, Helenore, Nera, Luna, Livana, Kiera
Hi all! I just wanted to say thank you to everyone who helped us - either by helping us veto a name, or by giving us new names and new types of names to consider. We had no clue if we were having a boy or a girl, so we went into the hospital with a long list of possible names. Well, we had a boy! He was born on his due date, April 22. He was 7lb 11oz and 21inches. I delivered him VBAC after having both the on call doctor and midwife try to convince me to have another c-section. Anyway, after two days, we settled on a name - Thaine Alasdair! He is perfect and we all love his name. Neither name was on our list, but we kept coming back to this forum to read all of your suggestions, check out meanings, etc. so thanks again to all of you!
Congratulations and lovely name!