Model Entity Representation of an Organigram
I think you need to do as follows. Create a Person entity with data fields such as id, name, address and create another entity Person-Relationship with data fields such as pr-id, rel-type with instance of grandfather, father, etc...The physical data model might look as follows,   

pr_type     
{      
     pr_id(pk), pr_type    
}     

person      
{      
     person_id(pk), pr_id(fk),  person_name   
}


Here, pr_type data field may contain the entities such as great grandfather, grandfather, father, son, etc...

I hope this will give some understanding. Thanks.