Custom 'natural' sort on complex object

[Dazfl]

I have a complex object that I would like to perform a 'natural' sort against and I've come to the conclusion that I need create a custom sort method (ISieveCustomSortMethods).

My object looks something like this (I'm just using a basic representation here) ...

{
    "entities": [
        {
            "entity": {
                "id": 123,
                "subEntities": [
                    {
                        "id": 234,
                        "title": "Sub-entity 234 title"
                    },
                    {
                        "id": 345,
                        "title": "Sub-entity 345 title"
                    }
                ]
            }
        },
        {
            "entity": {
                "id": 321,
                "subEntities": [
                    {
                        "id": 432,
                        "title": "Sub-entity 432 title"
                    },
                    {
                        "id": 543,
                        "title": "Sub-entity 543 title"
                    }
                ]
            }
        }
    ]
}

I would like to perform a natural sort on the subEntities title field. I realise that subEntites is an array, but I only need to perform the sort against the first sub-entity.

As an example, if I have a list of titles like - Title 1, Title 101, Book, Title 2, Study
... then the natural sort will produce a result like - Book, Study, Title 1, Title 2, Title 101

I'm wondering if anyone has solved a problem like this before, or may have some suggestions? I should add, that I'm trying to do this in conjunction with Entity Framework Core.