Insert/Add new entity with nested children entities to DB using Entity Framework Core - entity-framework

Question

Here are Entities:
public class Entity
{
public int Id { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime? ModifiedOn { get; set; }
}
public class EntityBase : Entity
{
[ForeignKey("CreatedBy")]
public int CreatedById { get; set; }
public User CreatedBy { get; set; }
[ForeignKey("ModifiedBy")]
public int? ModifiedById { get; set; }
public User ModifiedBy { get; set; }
}
public class ProjectRequest : EntityBase
{
public string RequestTitle { get; set; }
public string RequestType { get; set; }
...
public virtual ICollection<Material> Materials { get; set; }
public virtual ICollection<Translation> Translations { get; set; }
}
public class Material : EntityBase
{
[ForeignKey("ProjectRequest")]
public int ProjectRequestId { get; set; }
public virtual ProjectRequest ProjectRequest { get; set; }
...
public virtual ICollection<Translation> Translations { get; set; }
}
public class Translation:EntityBase
{
[ForeignKey("ProjectRequest")]
public int ProjectRequestId { get; set; }
public virtual ProjectRequest ProjectRequest { get; set; }
[ForeignKey("Material")]
public int MaterialId { get; set; }
public virtual Material Material { get; set; }
public string ProductMasterText { get; set; }
[MaxLength(40)]
public string ShortDescription { get; set; }
public string MasterDescriptionLine1 { get; set; }
public string MasterDescriptionLine2 { get; set; }
public string MasterDescriptionLine3 { get; set; }
public string LanguageCode { get; set; }
}
No modifications has been done to these entities using fluent API.
Now, whenever I try to insert object of type ProjectRequest with Materials and Translations nested in it, in Translation objects ProjectRequestId is set to 0.
Following is sample Change Tracker snapshot:
Can anyone help me on this? Why ProjectRequestId is 0 but MaterialId properly assigned in Transaltion objects?