Foster parent
From Tardis Wiki, the free Doctor Who reference
A foster parent was one who acted as a caregiver, without legally adopting the child.
Bill Potts was brought up by her foster mother, Moira, after her birth mum died in Bill's infancy. (TV: The Pilot)
Matron Cofelia, of the Five-Straighten Classabindi Nursery Fleet, chose her human alias, "Miss Foster", as a reference to this role, as in fact she was fostering million of Adipose children. (TV: Partners in Crime)
