Parse this person name:

Siem Vallenduuk (1251-1308, flourished 1274-1284)
user
first_name: Siem
last_name: Vallenduuk
middle_names: []
temporal:
- start: 1251
  end: 1308
  type: life_span
- start: 1274
  end: 1284
  type: flourished
titles: []
extra_info: []
assistant