I think in Addams Family Values (the second film) the baby was called Pubert, which isn’t as good as these suggestions imo.
Speaking of, I don’t actually have any, but a lot of these are either on my gp list, or actual list 
. Maybe [name_f]Alchemy[/name_f] or [name_u]Nyx[/name_u]?
Thank you! 
I was imaging Thirteen as a girl too for some reason - maybe it’s the -een ending like Doreen, Maureen, etc.? Mazikeen is a good shout! And I love Malady and Dismay a little too much - why do they sound like such lovely names, haha. Dudley makes for a great pair with Pugsley, and yes, Wyborn is perfect! And Daffodil is so deliciously ironic - sweet sound and innocent looking flower but actually poisonous. 
Could lend itself to really cool character design.
@clair.de.lune Macabre is dashing - can’t decide if I like it better for a boy or a girl! And Dreda feels like a fun, dark twist on Brenda.
@katinka Ooh, Maudlin! Sounds so dark and devious in this context. The “anti” part makes Antimony sound appropriately menacing, and I love the werewolf feel of Wolfsbane and Wilding.
@VioletMoon I agree, Gloom and Agony would be the perfect Addams twins! Also love the elegance of Despair and Obscenity.
@acajou I love that you have an Addams family esque imaginary family member. Aloysius works so well. Rubella is maybe my favourite girl name suggestion so far - has that Italian flair with the -Bella ending and an infectious disease makes for such a perfect Addams family name.
I can so easily imagine this sibset running around the graveyard together!
@mololy Aww, Dreary is so cute - like dearie but not. 
I also love Vlad, Nettle, and Morningstar.
@Myosotis Yeah, we have definitely come up with way better sibling names here! I noticed quite a few suggestions I’d be happy to add to my actual list too, haha - we must be goth at heart. Alchemy is a GP of mine too - just love the historical feel of it. 
Alchemy Addams has a great ring to it.
[name_m]Just[/name_m] had the thought of [name_m]Friday[/name_m] and Thirteen for twins! A little too on the nose, maybe?
my all time favourite movies!
[name_u]Salem[/name_u]
[name_u]Shelley[/name_u] (after [name_f]Mary[/name_f] Shelley?)
Catacomb ‘Cate’
I think it’s cute! I was playing around with the idea of Thirteen in Latin as well, Trecedim. Friday in Latin is dies Veneris (Venus’s day), so Trecedim and Veneris could also work! Or Thirteen and Venus. 
They’re so good. Shelley Addams is absolutely perfect! And I love the idea of introducing yourself as “Cate”. “Short for Catherine?” “No, Catacomb”.
[name_m]Ichabod[/name_m]
[name_f]Ludivine[/name_f]
Mandrake
Montresor (like the guy from The Cask of Amontillado)
Nightfall
[name_u]October[/name_u]
Pennsylvania
[name_f]Ravenna[/name_f]
[name_f]Sabrina[/name_f]
[name_u]Salem[/name_u]
[name_u]Snapdragon[/name_u]
[name_m]Thornton[/name_m]
[name_u]Twilight[/name_u]
[name_f]Vermilion[/name_f]
Cemetery
Necromancy
Ghastly
Darkness
Moonlight
Grim (Grimsley?)
[name_f]Mystery[/name_f]
Specter
Hauntley?
@VTW These are great! Grimsley and Hauntley are adorable, and I love [name_u]Twilight[/name_u], [name_f]Mystery[/name_f] and Cemetery. Quirky word names really feel like the way to go. The [name_m]Edgar[/name_m] [name_m]Alan[/name_m] [name_u]Poe[/name_u] connection with Montresor works so well within the Netflix show’s universe specifically.
I’m super late but I wanna hop all over this thread!
Scorpius
Velvet
Lucentia
Persephone
Percival
Dusk
Vale
Argyle
Désolée
Rue
Signus
Orion
Lupin
Monoceros
Cetus
Maven
Cordelia
Calico
Eloise
Horizon
Zenith
Eleonora
@solara Oohh I am loving the sound of [name_f]Velvet[/name_f] Addams, [name_u]Dusk[/name_u] Addams, and Signus Addams.
I love Thirteen!
Some other suggestions:
[name_f]Persephone[/name_f]
Hel (norwegian goddess of death)
Thanatos (greek god of death)
[name_m]Castor[/name_m]
Nightshade
Corvus (means crow)
Frankenstein
[name_f]Styx[/name_f]
[name_u]Mercury[/name_u]
[name_u]Salem[/name_u]
[name_m]Lucifer[/name_m]
[name_u]Love[/name_u] these! Draconian or Draconia popped to mind 
or how about Ruthless and Merciless (Ruthie and Mercy) for twin girls
I’d go [name_m]Misery[/name_m], it’s adorable.
Me trying to makeup good witch/wizard names:
Octoria, Nocturn, Noctem, Moonlit, Moony, [name_u]Hallow[/name_u], Hollow, Fall, [name_f]Eve[/name_f], [name_f]Sylvie[/name_f], [name_f]Phryne[/name_f], [name_u]Elia[/name_u], [name_u]Lyre[/name_u], Graven, Shaft, Tuft, Place, [name_m]Shady[/name_m], Gaunt, Bones, [name_m]Carver[/name_m], [name_u]Woodland[/name_u], [name_m]Hatcher[/name_m], [name_f]Cloudy[/name_f], Bones, [name_u]Raven[/name_u], Pale, [name_f]Doe[/name_f], [name_m]Hart[/name_m], [name_f]Crescent[/name_f], Norse, Botany, [name_f]Willa[/name_f], [name_f]Lullaby[/name_f], [name_m]Fields[/name_m], [name_m]Crow[/name_m], Mugs, Faint, Doze, Flicker, [name_u]Flame[/name_u], Hearth, Ashen, [name_m]Caliber[/name_m], [name_m]Eros[/name_m], [name_u]Rogue[/name_u], [name_m]Ransom[/name_m], [name_m]Riot[/name_m], [name_f]Vaeda[/name_f], [name_u]Sutton[/name_u], [name_m]Daemon[/name_m], [name_m]Fitz[/name_m], [name_f]Inga[/name_f], Curselle, Dizzy, Owla, [name_f]Evening[/name_f], Crowchild… Hmm got kinda crazy but ya hahah
@highhippogriff I am so here for Hel! One of the coolest goddesses for sure. Nightshade, Mercury, and Salem also sound absolutely perfect to me.
I am in love!
@xXBelladonnaXx Agreed - Misery Addams is perfectly cute and spooky.
@Yolooo These are so good - I’m particularly into Moonlit, Hollow, Mugs (matches brother Pugsley so well), Curselle, and Crowchild. And Lullaby is so fun, a sweet sound and meaning, but using it in this context gives it a dark twist.
[name_m]Just[/name_m] had another thought on this topic: Sepulchre
This was fun, may come back & add more!
Didn’t read through them all, but love the ideas of Alchemy, Nyx, & Noctem!
Fem.
Corva
Eris (Greek goddess of discord)
Discordia (Roman goddess of discord)
Hel / Hella (Norse goddess of the dead)
Melinoë (Greek goddess of ghosts, nightmares, madness, & funerary rites)
Melpomene (Greek muse of tragedy)
Saturnalia
Serpentine
Vespera (Latin for dusk)
Unfortuna
Neutral
Albatross (symbol of a burden or curse)
Corvid / Corvidae / Corvus
Moros / Morose (Greek spirit of doom / word meaning sullen)
Nox (Roman goddess of the night)
Saturnine / Saturninity (meaning gloomy or to suffer from lead poisoning)
Sparrow (bonus: sounds like “sorrow”)
Masc.
Harbinger
Severus
The Saturn names are probably too close to Wednesday, but still including them for “the vibes”
Nightmare!
Odile. 
The black swan from Swan Lake.
Persephone, queen of the underworld in Greek mythology
Chaos, personification of nothingness
[name_f]Wednesday[/name_f]: based on the nursery rhyme line: “Wednesday’s child is full of woe”.
Pugsley: “stomach pump” in Bulgarian.
[name_f]Delta[/name_f]
Number 4 is considered unlucky due to how similar it sounds to the word “death” in Chinese. [name_f]Delta[/name_f] means 4, the unlucky number.
[name_u]Mirin[/name_u]
Translates to “death” in Kurdish.
[name_u]Mel[/name_u]
Short for Melancholy, a feeling of pensive sadness
[name_u]Issa[/name_u]
Translates to “sad” in Maltese.
[name_u]Midnight[/name_u]
When I came across this name I instantly thought of the quote “Nothing good ever happens after midnight”
[name_u]Oleander[/name_u]
Of course, after one of many deadly plants.
[name_f]Belladonna[/name_f]
The Latin name of the deadly nightshade plant is atropa belladonna. Of course, the nightshade part may also be a reference to the recent series.
Gwenwyn
Means “poison/venom” in Welsh.