Well, actually lots of families nowadays are mixed (north+south) because after WW2 ended, Italy was an extremely poor and devastated country. The north has always been more advanced than the south, so usually women from the south would try to marry a man from the north in hopes to lead a better life.
Nowadays in our generation, perhaps a mixed couple wouldn’t be seen as positively as in our grandparents’ generation (the boomers hehe).
Well, if it helps you, I’m pale as a ghost and I’m from Milan (north). However, it’s worth noting that I’m 3/4 northerner and 1/4 southerner. My grandma (from the south) isn’t as pale as I am, but she isn’t dark either, she’s quite light in complexion. All this to say, your character can literally be from everywhere you want. You can use my city if you like!