How did Laurie's parents die?

We are not told how Laurie's parents die.

"I am not sure, but I think it was because his son, Laurie's father, married an Italian lady, a musician, which displeased the old man, who is very proud. The lady was good and lovely and accomplished, but he did not like her, and never saw his son after he married. They both died when Laurie was a little child, and then his grandfather took him home.