JSON.net Deserialize json text from flat to nested object

I have the following JSON text:

{
    "personAFirstName": "John",
    "personALastName": "Smith",
    "personBFirstName": "Alexander",
    "personBLastName": "Hamilton"
}

And want to deserialize it to the following object shape:

{
    "a": {
        "firstName": "John",
        "lastName": "Smith"
    },
    "b": {
        "firstName": "Alexander",
        "lastName": "Hamilton"
    }
}

Is there a simple way using Newtonsoft.Json Attributes or do I need to do something more complicated than that on the class specification?

class Relationship 
{
    Person a { get; set; }
    Person b { get; set; }
}

class Person
{
    string firstName { get; set; }
    string lastName { get; set; }
}