Their surname is [name_m]Fox[/name_m] 
Now I’m really not sure what names I should use since the name I’m considering for my main character is made up. Well, kind of. She is transgender and her birth name was [name_m]Sebastian[/name_m] [name_m]David[/name_m]. I am most likely going to have her go exclusively by Sebby. I was going to give her a completely different name (probably [name_f]Daphne[/name_f]) but I prefer creating my own names if I can and I like having something different for my main characters. But the problem is, I can not imagine what I would call her siblings.
Originally they were going to have softer-sounding, classic but not too common names. I don’t think her name fits into those categories. Oh, I better say this before I forget…there are six siblings. Sebby is the eldest, then it goes girl, girl, boy, girl, boy and another girl. So, five girls and two boys. The names I really want to use are [name_f]Ellen[/name_f] and [name_m]Crispin[/name_m]. I don’t know why, I have a real obsession with those names, haha. I kind of like [name_f]Rosamund[/name_f] too. That was supposed to be the name for the second eldest girl (after Sebby) but it doesn’t really suit her. She’s popular, sort of preppy and a stereotypical “mean girl.” The third girl (who I want to be [name_f]Ellen[/name_f]) is very shy and intelligent, more of a caretaker and a total wallflower. The first boy is very theatrical and energetic/rowdy. Fourth girl is awkward and geeky, she’s rather sensitive and a little self-conscious I think. Now the second boy and sixth child is the one I wanted to name [name_m]Crispin[/name_m]. I wanted his nickname to be [name_u]Kit[/name_u] but I don’t even know if that is a nickname for [name_m]Crispin[/name_m]? And I think “[name_u]Kit[/name_u]” and “[name_m]Fox[/name_m]” and too cheesy together 
He is blind. He and the youngest girl are like partners in crime, they’re both very curious and have good hearts. The youngest girl is also very feminine, essentially a “girly girl.”
So, does anyone have any suggestions for my sibset? And are [name_f]Ellen[/name_f] and [name_m]Crispin[/name_m] alright? By the way, I don’t think any more names ending in -en, -an or -in are wise because I don’t want to fall into a theme. Thanks! 
I think that, because your main character’s birth name was [name_m]Sebastian[/name_m] [name_m]David[/name_m], I’d expect his - and later, her - siblings to be named something equally as classic, though not particularly common.
Off the top of my head, if I were to name the siblings, they’d be:
[name_m]Sebastian[/name_m] [name_m]David[/name_m] ‘Sebby’
[name_f]Vivienne[/name_f] [name_f]Sarah[/name_f] ‘[name_f]Vivi[/name_f]’
[name_f]Penelope[/name_f] ‘[name_f]Nell[/name_f]’/[name_f]Rosamund[/name_f] ‘[name_f]Rosie[/name_f]’ [name_f]Grace[/name_f]
[name_m]Theodore[/name_m] [name_u]James[/name_u] ‘[name_u]Teddy[/name_u]’ OR [name_m]Charles[/name_m] [name_m]William[/name_m] ‘[name_u]Charlie[/name_u]’
[name_f]Angelica[/name_f] [name_f]Louise[/name_f] ‘[name_u]Angie[/name_u]’ OR [name_f]Beatrice[/name_f] [name_f]Lucy[/name_f] ‘[name_f]Bea[/name_f]’ OR [name_f]Lillian[/name_f] [name_f]Kate[/name_f] ‘[name_f]Lily[/name_f]’
[name_m]Alexander[/name_m] [name_m]Thomas[/name_m] ‘[name_u]Alex[/name_u]/[name_m]Xander[/name_m]’
‘Sebby, [name_f]Vivi[/name_f], [[name_f]Nell[/name_f] OR [name_f]Rosie[/name_f]], [[name_u]Teddy[/name_u] OR [name_u]Charlie[/name_u]], [[name_u]Angie[/name_u] OR [name_f]Bea[/name_f] OR [name_f]Lily[/name_f]] and [name_u]Alex[/name_u]/[name_m]Xander[/name_m]’
However, if you were to use [name_f]Ellen[/name_f] and [name_m]Crispin[/name_m] (which I think are completely fine names, by the way, just not what I’d personally expect siblings to [name_m]Sebastian[/name_m] to be named), I’d suggest sightly longer and classic names for the boys, and shorter for the girls:
[name_m]Sebastian[/name_m] [name_m]David[/name_m] ‘Sebby’
[name_f]Charlotte[/name_f] [name_f]Sarah[/name_f] ‘[name_f]Lottie[/name_f]’ (though I like [name_f]Vivienne[/name_f] [name_f]Sarah[/name_f] for this character, it does end in an ‘en’ sound - you could use [name_f]Angelica[/name_f] nn [name_u]Angel[/name_u] [or just [name_u]Angel[/name_u]] for the irony that her nickname is the opposite of her personality)
[name_f]Ellen[/name_f] [name_f]Katherine[/name_f]
[name_m]Theodore[/name_m] [name_u]James[/name_u] ‘[name_u]Teddy[/name_u]’ ([name_m]Charles[/name_m] is too similar to [name_f]Charlotte[/name_f] for my tastes)
[name_f]Clara[/name_f]/[name_f]Lucy[/name_f] [name_f]Beatrice[/name_f] OR (any of the suggested above)
[name_m]Crispin[/name_m] [name_m]Thomas[/name_m] (I like the nickname [name_m]Pip[/name_m] for [name_m]Crispin[/name_m], as I don’t think [name_u]Kit[/name_u] fits entirely - what do you think of [name_m]Atticus[/name_m] nn [name_u]Kit[/name_u]? [name_m]Christopher[/name_m]? And [name_m]Crispin[/name_m] ‘[name_u]Kit[/name_u]’ [name_m]Fox[/name_m] does sound slightly cheesy, though it could work… Is the last name set?)
Good luck with your story!
I think [name_f]Ellen[/name_f] and [name_m]Crispin[/name_m] are all right. [name_m]Crispin[/name_m] nn [name_u]Kit[/name_u] might not be “correct”, but totally works. I wouldn’t worry about [name_u]Kit[/name_u] and [name_m]Fox[/name_m], they aren’t really going to be said together are they? It’ll be either [name_u]Kit[/name_u], [name_m]Crispin[/name_m], or [name_m]Crispin[/name_m] [name_m]Fox[/name_m], but hardly ever [name_u]Kit[/name_u] [name_m]Fox[/name_m].
So, the sibset might be…
Sebby (or [name_f]Daphne[/name_f])
[name_f]Rosamund[/name_f], [name_f]Victoria[/name_f], [name_f]Antonette[/name_f], [name_f]Jessica[/name_f] or [name_f]Tiffany[/name_f]
[name_f]Ellen[/name_f]
[name_m]Robert[/name_m] “[name_m]Rob[/name_m]”, [name_m]Julian[/name_m], [name_u]Carson[/name_u], [name_m]Patrick[/name_m] or [name_m]Frederick[/name_m] “[name_m]Fred[/name_m]”
[name_f]Amber[/name_f], [name_f]Judith[/name_f], [name_f]Mary[/name_f], [name_f]Rachel[/name_f], [name_f]Jane[/name_f] or [name_f]Philippa[/name_f]
[name_m]Crispin[/name_m]
[name_f]Isabelle[/name_f], [name_f]Lily[/name_f], [name_f]Faye[/name_f] (maybe not with that lastname though), [name_f]Rose[/name_f], [name_f]Evie[/name_f] or [name_f]Grace[/name_f]
[name_m]Sebastian[/name_m] [name_m]David[/name_m] / Sebby: I thought I’d look up some feminine names that contain “[name_m]Seb[/name_m]”, or that could work with the nickname Sebby. I have [name_f]Daphne[/name_f] as the middle name, but it’s not finite.
[name_f]Sebina[/name_f] [name_f]Daphne[/name_f] [name_m]Fox[/name_m]
[name_f]Jessebel[/name_f] [name_f]Daphne[/name_f] [name_m]Fox[/name_m]
[name_f]Sister[/name_f] 1: I’m going for intimidating, “80’s mean-girl”-type names.
[name_f]Isobel[/name_f] [name_f]Katherine[/name_f] [name_m]Fox[/name_m]
[name_f]Jennifer[/name_f] [name_f]Iris[/name_f] [name_m]Fox[/name_m]
[name_f]Genevieve[/name_f] [name_f]Sara[/name_f] [name_m]Fox[/name_m]
[name_f]Farrah[/name_f] [name_f]Josephine[/name_f] [name_m]Fox[/name_m]
[name_f]Sister[/name_f] 2: I’m sticking with common names that are pretty but not totally memorable, to go with her wallflower personality.
[name_f]Ellen[/name_f] [name_f]Mary[/name_f] [name_m]Fox[/name_m]
[name_f]Ellen[/name_f] [name_f]Abigail[/name_f] [name_m]Fox[/name_m]
[name_f]Ellen[/name_f] [name_f]Margaret[/name_f] [name_m]Fox[/name_m]
Brother 1: Since he’s very theatrical, I thought he’d like to have a long, handsome name.
[name_u]Lawrence[/name_u] [name_u]Parker[/name_u] [name_m]Fox[/name_m]
[name_m]Malcolm[/name_m] [name_m]Henry[/name_m] [name_m]Fox[/name_m]
[name_m]Nathaniel[/name_m] [name_m]Graham[/name_m] [name_m]Fox[/name_m]
[name_f]Sister[/name_f] 3: I’m thinking of classic, delicate names for her.
[name_f]Alice[/name_f] [name_f]Patricia[/name_f] [name_m]Fox[/name_m]
[name_f]Violet[/name_f] [name_f]Lydia[/name_f] [name_m]Fox[/name_m]
[name_f]Cecily[/name_f] [name_f]Miranda[/name_f] [name_m]Fox[/name_m]
Brother 2: [name_m]Just[/name_m] some names I thought would sound nice with [name_m]Crispin[/name_m].
[name_m]Crispin[/name_m] [name_m]Oliver[/name_m] [name_m]Fox[/name_m]
[name_m]Crispin[/name_m] [name_m]Gregory[/name_m] [name_m]Fox[/name_m]
[name_m]Crispin[/name_m] [name_m]Timothy[/name_m] [name_m]Fox[/name_m]
Potential nicknames for [name_m]Crispin[/name_m] could be [name_u]Cris[/name_u] or [name_m]Kip[/name_m]. [name_u]Kit[/name_u] works for the name itself but probably not with the last name [name_m]Fox[/name_m].
[name_f]Sister[/name_f] 4: I think [name_f]Rosamund[/name_f] would be perfect for her! The name just exudes feminine and girly to me.
[name_f]Rosamund[/name_f] [name_f]Michelle[/name_f] [name_m]Fox[/name_m]
[name_f]Rosamund[/name_f] [name_f]Louise[/name_f] [name_m]Fox[/name_m]
[name_f]Rosamund[/name_f] [name_f]Elizabeth[/name_f] [name_m]Fox[/name_m]
I could honestly go on and on for each of these names but my post is already pretty long so I’ll cut it off here. I hope this helps a bit.