8 Simple Rules comes to mind.
Everyone in the family has either brown hair or red hair, yet there was one blonde girl. I'm guess they just need a "hot daughter" for the show.
It was like that on Reba, too. Blonde daughter (Cheyenne), red-haired daughter (Kyra), and brunette son (Jake). Jake was the odd one out. Reba's a red-head and Brock was a blonde/strawberry blonde. I do think the actress who played Kyra really looked like she could be Reba's daughter.
Who knows with genetics, though. My mom (red hair and blue eyes) and my dad (black hair and brown eyes) produced three brunettes (two with brown eyes, one green) and two blondes (both blue eyes).
A bit of good casting, I think Alias was usually okay with casting families (Nadia notwithstanding.) Jennifer Garner really does look like what a child of Lena Olin and Victor Garber would look like.