[name_m]Hi[/name_m] Berries! I have two sons, [name_u]Bryce[/name_u] (4y) and [name_m]Theodore[/name_m] “[name_u]Teddy[/name_u]” (8m.) I want to start trying another baby in [name_u]December[/name_u]. I want a close age gap this time around. This being my last child, I really want a girl. I picture their names on a [name_u]Christmas[/name_u] card like ,“[name_u]Love[/name_u], [name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and ???” I want them to look good on paper and when I introduce them. For a boy, I love the name [name_m]Dashiell[/name_m] “[name_u]Dash[/name_u]”. I love the name [name_f]Kitty[/name_f], just [name_f]Kitty[/name_f], for a girl. Does it sound too close to [name_u]Teddy[/name_u]? I like leaned back and fun names for girls. But something that will also age well and at least semi-match my boys’ names. Something containing a “Y” is preferable! Thanks guys!
I was a little perplexed how you came up the your sibset [name_u]Bryce[/name_u] and [name_m]Theodore[/name_m]. Were your boys names to honor family members? One being trendy and one traditional they are fairly different. If going traditional like [name_m]Theodore[/name_m], with your girl, I’d go with [name_f]Katherine[/name_f] or [name_f]Kathleen[/name_f] using the cute nn [name_f]Kitty[/name_f]. If going more trendy like [name_u]Bryce[/name_u], then maybe [name_f]Katrina[/name_f] or [name_f]Katrin[/name_f] would be the way to go to get to [name_f]Kitty[/name_f]. Personally, I wouldn’t use [name_f]Kitty[/name_f] as a fn with your sibset, but it’s definitely a usable nn.
I must say that [name_f]Kitty[/name_f] is a fine name. 
My nickname is [name_f]Kitty[/name_f], but my formal name is [name_f]Catherine[/name_f]. [name_u]Bryce[/name_u], [name_m]Theodore[/name_m], and [name_f]Catherine[/name_f] aka [name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Kitty[/name_f] are the bee’s knees! Other suggestions:
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Lucy[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Cecily[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Katya[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Posy[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Romilly[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Maisy[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Molly[/name_f]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_u]Romy[/name_u]
[name_u]Bryce[/name_u], [name_u]Teddy[/name_u], and [name_f]Milly[/name_f]
I like [name_f]Kitty[/name_f], it’s very cute and goes well with your son’s names. I like the suggestions above!
Others:
[name_f]Hattie[/name_f]
[name_f]Mamie[/name_f]
[name_f]Minnie[/name_f]
[name_f]Rosie[/name_f]
[name_u]Josie[/name_u]
[name_u]Frankie[/name_u]
[name_f]Lottie[/name_f]
[name_f]Daisy[/name_f]
[name_u]Ruby[/name_u]
Personally, I wouldn’t. At face value, it’s a very cute name, but I feel like it has the potential to be very sexualized, and I just wouldn’t want to go there. I like [name_u]Kit[/name_u] by itself, but [name_f]Kitty[/name_f] is a different story, for me.
I had [name_u]Bryce[/name_u] when I was 19. I wasn’t really thinking about sibset combos back then or my naming style. I just chose what I liked. Both of their middles are family names. I chose [name_m]Theodore[/name_m] solely for the nickname [name_u]Teddy[/name_u]. I think [name_u]Bryce[/name_u] and [name_u]Teddy[/name_u] go together well! 
Thank you for the suggestions thus far! I do like the name [name_f]Catherine[/name_f]. 