Answer: Adult that are related closely to child for taking care and rearing
Explanation: Biological parent are defined as caregiver of the child whose gametes were responsible for child's birth. But in general terms parent is defined as the adult caretaker of the child because of being close and being their first guardian .
The mentioned situation about three cases of Alicia, Jee and Tom in the question considers all the adults taking care of them as their parents respectively .
Even though Alicia is adopted and does not have biological parents but she has to regard them as her parent because they are the guardian taking care of her.
Jee has two mothers and Tom has unmarried mother who are also considered as parents of them because they are rearing them and providing care as an close adult.