Glados is the remains of the conciousness of Caroline, Cave Johnson's personal assistant and possible lover/wife. In half-life 2 there's a black mesa file about Chell stating that her name is Chell Johnson and that Caroline is her mother. Furthermore, Caroline and Chell look remarkably similar, and the turret orchestra is Cara Mia Addio, which translates to Good Bye my Dear. furthermore, Chell is stated by name in the song and the reprise refers to her as "mah bambina" which means "my little girl"
their relationship isn't something lovely dovy. their relationship is a deep seeded physiological need, Chell is completely ignorant of the world above her, and GLaD0S has a need to test, tests which Chell can always do.
their relationship is like Sherlock and Watson not sexual, but an emotional and physiological need for the other.
caroline looks remarkably like chell, sharing so much in the way of cheek bones and figure as well as hair color. on top of that, the song the turrets sing is called "oh my daughter."
not saying it's not beyond the realm of possibility, but canonical the two have yet to be officially confirmed as mother and daughter although if valve did go in that direction i would very much like it, would make their characters and relationship (in the platonic sense of course) more interesting