The scientific analysis that followed , strengthened the belief that the three skeletons in the grave are the remains of Birger jarl , his son duke Eric Birgersson and Birger 's wife Mechtild of Holstein .
Head entity: eric birgersson Q3486875 26 27
Tail entity: birger jarl Q316828 20 21
Relation (head \u2192 tail): P22
Inverse relation (tail \u2192 head): P40