This reminds me of a song called 'My Son David' which I heard many years ago. I don't know if it's Scottish or Welsh, but the first verse goes like this....

Oh, what's the blood that's on the stone, My son David, oh, son David, What's the blood that's on the stone, Come, promise, tell me true?

And it goes on to say that 'that's the blood of my grey mare', 'my brother John', 'my Lady wife' etc., but I can't remember it off-hand. There are quite a few songs of this ilk, 'Lord Edward' and 'My Son Henry' for instance. 'My Son David' beats them all hands down though!!