What does "how toward..." and "late addition" mean in this sentence?

"Around the time they first met, Daniel had told Mary Jane how toward the end of his parents’ lives—Daniel a late addition—his mother and father spoke only through the dog.> "

What does it mean "how toward the end of his parents' lives"?
Especially the meaning of "how toward"?

I've searched about the grammar of how, but all I could find was useless in this sentence.

Does it mean that " at the end of his parents' lives,his mother and father spoke only through the dog.considering the fact that Daniel was their last child"?

Solution 1:

It means that at the end of his parents' lives, his mother and father spoke only through the dog. See if reading it like this helps:

Around the time they first met, Daniel had told Mary Jane how—toward the end of his parents’ lives (Daniel being a late addition to the family)—his mother and father spoke only through the dog.