Kurt is voiced by Liam Garrigan.
Petrus is voiced by Steven Hartley.
Are you just cruising voice actors' social media and websites to find clues?
LOL - was on Twitter and saw the one about Vasco appear in my feed. And then noticed that Kezia Burrows comes up in a people Twitter search about Greedfall and I wondered why. I saw she is an actress and clicked on the link on her Twitter profile that takes you to her website. Her website mentions she is the voice of Siora.
And I was apparently bored this afternoon.