Parse this person name:

Siem van Kempen, 1906-1981, flourished 1923-1951
user
first_name: Siem
last_name: van Kempen
middle_names: []
temporal:
- start: 1906
  end: 1981
  type: life_span
- start: 1923
  end: 1951
  type: flourished
titles: []
extra_info: []
assistant