Serif has had a solid Windows vector drawing app (DrawPlus) for a long time. If I remember correctly, a group of ex-Xara developers moved to Serif to write it. Affinity looks similar, I would be surprised if they aren't based on the same codebase.
You're right that some Xara devs added to DrawPlus over the years, but the Affinity titles are fr fr fresh and have different goals and philosophy.