How old are Jurgis and Ona at the beginning of The Jungle?

At the beginning of The Jungle, Ona
is not yet sixteen years old.  Jurgis, by contrast, is quite a bit older.  It appears
that he is about 26 years old.

We can see Ona's age in the
very first pages of the book.  At the beginning of the book, she is getting married.  We
are told that she is only 15 at that point.  We can see this in the following
quote:

She was
so young—not quite sixteen—and small for her age, a mere
child...

We know that Jurgis
is quite a bit older than Ona is.  In Chapter 7, when Jurgis' father dies, we are
told

For
twenty-five years old Antanas Rudkus and his son had dwelt in the forest together, and
it was hard to part in this
way...

Since the book starts
with the family already in Chicago, that means that Jurgis was about 26 by the time the
book starts.