Two characters, that are siblings. [name]Both[/name] have medium-dark brown hair, hazel eyes, and freckles. Boy is smart, a reader, a thinker, a quiet leader; gentle and soft-spoken, but not shy. Tall with curly hair. Girl is younger than her brother, more outgoing and out-spoken. Snarky, a bit rough around the edges, but not unkind. A generally good student, but excels at math and science especially. Wears glasses, voracious reader.
I need help with these kids. I have no idea what to call them. For the boy I am just torn. Is he the trendy [name]Milo[/name]? The less-used [name]Kit[/name]? Is he the hipster-y [name]Atticus[/name]? Is he absolutely off-the-wall [name]Absalom[/name]? British-inspired [name]Hamish[/name]? And for his sister, I can’t even think of a name. It should be an established name, nothing made up or unheard of, but something less popular. Feminine, but by no means frilly. Something strong, and preferably without an easy nickname.
For the boy: [name]Grey[/name], [name]Finn[/name], [name]Greg[/name] / [name]Gregory[/name], [name]Michael[/name], [name]Frost[/name], [name]Kylan[/name], [name]Xander[/name], [name]Samson[/name], [name]Waylon[/name], [name]Weston[/name], [name]Jude[/name], [name]James[/name], [name]Jimmy[/name]? And the girl: [name]Beth[/name] / [name]Bethan[/name], [name]Ruth[/name], [name]Ruby[/name], [name]Joanne[/name], [name]Florence[/name], [name]Abbey[/name], [name]Kam[/name], [name]Livia[/name], [name]Preston[/name], [name]Mayer[/name], [name]Mona[/name], [name]Henny[/name], [name]Tori[/name], [name]Eve[/name], [name]Ava[/name]? 
[name]Hope[/name] these have given you some ideas.
Who are their parents? What kind of people are they and what are their passions? Are they traditional? [name]Do[/name] they feel a strong connection to their past/family? Are they workaholics? Did they abandon their kids? I always find that understanding who the parents are, who they were when they had their kids, what they wanted for their kids and whether they’re the type of people to reflect that in names–is helpful when naming.
Milo - great name for parents who are urban or a bit on the non-traditional side but still want something interesting. I can see a Milo with a sister Phoebe or Erin.
Kit - good option for both traditional parents (who named him K/Christopher and he picked Kit) or parents who purposely wanted a unique nickname. Sister could be Alexandra, Samantha (nn Sam), Stephanie, Elizabeth–something else that’s long and with good nn’s
Atticus - interesting, and definitely for parents who are more extreme and want something very different. Sister could be Petra, Clementine, Lavinia, Octavia, Junia
Absalom - strong impression here, very heavy and Biblical and literary. Sister might be Zilpah, Prudence, Winifred, Jemima, Priscilla.
Hamish - not my favorite, but if it’s from their family or important to their cultural story then it might work. Sister could be Tamsin, Freya, Bryony, Phillipa, Imogen.