What was the relationship between Siward and Sweyn Forkbeard and their dealings with Scotland under King Macbethad mac Findláech?

Factual Questions
1

What was the relationship between Siward and Sweyn Forkbeard and their dealings with Scotland under King Macbethad mac Findláech ?

2

Sweyn was quite dead before Macbeth or Siward flourished.