Yes. The IRS requires a separate W-8BEN or W-9 for each beneficial owner.
IRS reference: “Who Must Provide Form W-8BEN,” IRS Instructions, Pages 2–3. Ultimately the K-1 will name both partners.
IRS reference: “Who Must Provide Form W-8BEN,” IRS Instructions, Pages 2–3. Ultimately the K-1 will name both partners.