Hey all! We have boy/girl twins due in [name_u]January[/name_u]. Really like the boy name [name_m]Dax[/name_m] but struggling to find a girl name we love. We already have two boys ages 6&4… they are named [name_m]Grant[/name_m] & [name_m]Griffin[/name_m] so I really think the twins should share the same letter.
What do you all think of [name_m]Dax[/name_m] & [name_f]Della[/name_f]?
I love [name_f]Della[/name_f]. I think that’s a good choice.
Other ideas:
[name_f]Delia[/name_f]
[name_f]Delilah[/name_f]
[name_f]Dinah[/name_f] (with dee-nah pronunciation)
[name_f]Dahlia[/name_f]
[name_f]Daisy[/name_f]
I really like [name_m]Dax[/name_m] and [name_f]Della[/name_f]!
Other girl D names:
[name_u]Drew[/name_u]
[name_u]Dusty[/name_u]
Dusky
[name_f]Delores[/name_f]
[name_f]Delphi[/name_f] / [name_f]Delphie[/name_f]/ [name_f]Delphine[/name_f]
[name_f]Dawn[/name_f]
[name_f]Darla[/name_f]
[name_f]Daphne[/name_f]
[name_f]Demi[/name_f]
[name_f]Darcie[/name_f]
[name_f]Dora[/name_f]
[name_f]Dionne[/name_f]
[name_f]Daria[/name_f]
[name_u]Delaney[/name_u]
The shared initial is absolutely not a must!
Your style is modern, straightforward and last name-y; that said, [name_f]Della[/name_f] doesn’t go too badly with [name_m]Grant[/name_m], [name_m]Griffin[/name_m] and [name_m]Dax[/name_m].
I do like a bit better pp’s suggestion of [name_u]Drew[/name_u]. [name_f]Daisy[/name_f] would also go well.
Other ideas with D: [name_f]Diana[/name_f] (strong, recognizable, has A and I), [name_u]Devin[/name_u], [name_u]Dallas[/name_u].
Other ideas without D: [name_f]Poppy[/name_f], [name_u]June[/name_u]/[name_f]Juno[/name_f], [name_f]Hope[/name_f], [name_f]Eva[/name_f]/[name_f]Eve[/name_f]/[name_f]Ava[/name_f], [name_f]Cleo[/name_f], [name_f]Ada[/name_f] (it has the D and the same length as [name_m]Dax[/name_m], though I don’t know if it’s not too soft for you), [name_u]Aspen[/name_u], [name_f]Brynn[/name_f], [name_u]Hadley[/name_u], [name_u]Cali[/name_u], [name_u]Carson[/name_u], [name_u]Harper[/name_u]/[name_f]Harlow[/name_f]/[name_u]Harley[/name_u], [name_f]Iris[/name_f], [name_f]Ivy[/name_f], [name_f]Nova[/name_f], [name_u]Marley[/name_u], [name_f]Thea[/name_f], [name_u]Tatum[/name_u], [name_u]Wren[/name_u], [name_u]Eden[/name_u], [name_f]Ella[/name_f].
My favorites with [name_m]Grant[/name_m], [name_m]Griffin[/name_m] and [name_m]Dax[/name_m] are [name_f]Poppy[/name_f], [name_f]Hope[/name_f] and [name_f]Ivy[/name_f].
[name_m]Dax[/name_m] and [name_f]Della[/name_f] are both super cute! As are [name_m]Grant[/name_m] and [name_m]Griffin[/name_m]. 
Other pretty girl D names:
[name_u]Dylan[/name_u] (even though it’s mostly used for boys)
[name_f]Dahlia[/name_f]
[name_u]Darian[/name_u]
[name_u]Darcy[/name_u]
I like [name_m]Dax[/name_m] and [name_f]Della[/name_f]!
Other ideas:
[name_f]Deryn[/name_f]
[name_f]Delyth[/name_f]
[name_f]Drea[/name_f] (Dray-uh or [name_f]Dree[/name_f]-uh)
[name_f]Danielle[/name_f] / [name_f]Daniela[/name_f]
[name_f]Danica[/name_f]
[name_u]Dillan[/name_u]
[name_m]Daley[/name_m]
[name_f]Dolly[/name_f]
[name_f]Dottie[/name_f] / [name_f]Dot[/name_f] ([name_f]Dorothy[/name_f] could be full name?)
In addition to [name_f]Della[/name_f], I think [name_f]Drea[/name_f], [name_f]Danielle[/name_f], [name_m]Daley[/name_m], [name_f]Dolly[/name_f], and [name_f]Dottie[/name_f] go really well with [name_m]Dax[/name_m]. I also love [name_m]Grant[/name_m] and [name_m]Griffin[/name_m], btw!