De-serialise IReadOnlyList property in C# that cannot be set outside the class.

JSON_Deserialise_IReadOnlyList.cs

/* 
   How to de-serialise a property that returns an IReadOnlyList and shall not be set
   from outside?
*/
using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Text.Json.Serialization;

public class PersonClass
{
	public string Name { get; set;}
	public int Age { get; set;}
	
	protected List<string> children;
	public IReadOnlyList<string> Children 
	{ 
		get { return children.AsReadOnly(); }
		protected set { children = new List<string>(value); }
	}
	
	public PersonClass()
	{
		children = new();
	}
	
	[JsonConstructor]
	public PersonClass(IReadOnlyList<string> children) : base()
	{
		this.Children = children;
	}
	
	public override string ToString()
	{
		string ChildrenString = "";
		foreach(var c in Children)
			ChildrenString += c;
		return $"Name: {Name}, Age: {Age}, Children: {Children.Count} ({ChildrenString})";
	}
}

public class Program
{
	public static void Main()
	{
		var json = @"{""Age"":23, ""Name"":""Taro"", ""Children"": [""Ich"", ""Du""]}";
		var person = JsonSerializer.Deserialize<PersonClass>(json);
		Console.WriteLine(person.ToString());
	}
}