Petunia as a Squib??

[Brooks R]

No: HPFGUIDX 1638

I do not think that theory, interesting though it is, will work. 
There 
was just too much emphasis put in the 'Lily as wizard-capable off-
spring of Muggle parents' in Book Two, too much emphasis on Harry as
a 
good wizard and a good guy, descendant of such a reverse-of-a-squib,
to 
cheapen this theme by revealing that the 'truth' was different.

It also occurs to me that in a way, JKR is defending mixed marriages 
and her daughter in the mixed-wizard-muggle theme, not just having a 
general tolerance theme.  While a Portuguese man is obviously still a 
Caucasian European, (unless descended from someone who had returned
to 
Portugal from Brazil, posibly even with some 'slave' blood) there are 
'regional' ethnic characteristics that may can come through in 
appearance and heredity.  Even if JKR's marriage ended in divorce,
she 
may be defending her right to have entered into such a mixed marriage 
and having such a child!  Has anyone ever seen a pic of her daughter?

-Brooks