Just went to the SeaTac Centurion lounge. Two guests, regardless of relationship, per cardholder. There was a policy change in March. Before, all immediate family could enter - not anymore...at least at SeaTac
It's the primary cardholder plus two guests. I just did that yesterday with no additional charge.
The cardholder can bring up to two guests for free.
If you have minor children, I believe they will let the entire family in as well.
Up to 2 guests for free using a Platinum or Centurion card. Addl guests beyond those 2 are allowed based on capacity but they charge $50 per person for a day pass
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