YA/paranormal book about a boy who can take pictures of ghost in the Victorian? era. Helps a young black servant girl find out about her missing friend/employer. Spoilers

[Oneesha]

I remember he married the servant girl at the end and their daughter named after the girl's deceased friend who was sickly was begging him to take a photo of her in case she passed, but the MC was reluctant to due to him fearing what he might see in the photo.

[Rosa]

The Seer of Shadows

[Rosa]

Oneesha?

[Rosa]

?

[Courtney]

Rosa wrote: "?"
They were last active in June

[Rosa]

Yeah, I know.