Alex Taggart is the son of Samantha Taggart. He was born when Sam was fifteen years old. He suffers from diabetes. He was originally portrayed by Oliver Davis, but was replaced by Dominic Janes in Season 12.
When Sam starts working at County General Hospital, Alex is a young teenager. He tends to rebel against his mother, but befriends Dr. Luka Kovač and seems to respect his authority. Alex also seems to take an interest in medicine and anatomy. This, in part, leads to Sam and Luka entering into a relationship. Sam and Alex ultimately move in with Luka.
Alex cares for his father, Steve Curtis, despite Steve's irresponsible activities and leaving Alex and Sam alone. Whenever Steve returns to Chicago, he spoils Alex (often with stolen gifts) and wins his affections, to Sam's annoyance. When he leaves, he often steals things from Sam to sell to make ends meet.
Steve returns at one point and indicates that he is taking Alex with him. He also takes many of Luka's possessions from his apartment. Luka and Sam learn that Steve has a warrant out for his arrest and tell Steve to leave Alex alone and not to involve him in Steve's run from the law. Steve is ultimately arrested and sent to prison, but Sam keeps this a secret from Alex. Steve continues writing Alex as if he is on the road.
Sam and Alex move in, for a time, with a wealthy patient with a terminal disease that Sam meets in the ER who hires Sam part time to be a live-in caregiver.
Alex runs away and travels to Colorado in search of Steve. Sam and Luka scramble to locate Alex, as he does not have his diabetes medication with him, and could become unstable very quickly. After several bad leads, Sam finds Alex stable at a hospital where he tells her he can take care of himself. Sam breaks up with Luka because Alex can't cope with him anymore.
In season 12, Alex gets picked up from school by Mary, an accomplice of Steve's posing as a nurse at County. Mary helps Steve and another prisoner escape while they have been transferred from jail to County for medical treatment. She ties Alex up and puts him in a van. Steve and the others later kidnap Sam and Alex. In "Bloodline", Steve shoots his accomplices over a disagreement of the plan, and he rapes Sam. Later, while he sleeps, Sam gets his gun and shoots Steve. Sam later discovers that Alex saw her shoot Steve.
Alex continues to rebel, and later, playing with alcohol, accidentally sets the building on fire. He is sent to a special school for three weeks where he apologizes to his mom.
In season 15, Sam and Alex move in with Dr. Tony Gates, Sam's boyfriend, and Sarah, his ward. In a blizzard, Tony lets Sarah and Alex walk to a party, but an irresponsible Alex takes a friend's car home without a license and has an accident, Sam goes ballistic, but Alex later recovers and gets better.
Alex's age changes based on the needs of the storyline. When he is introduced in season 10, he is described as a "teenager." Two years later, when he runs away, he is referred to as "12 years old." If Alex was only 10 when introduced, that means his mother, who gave birth at age 15, should be less than three years out of nursing school, but she is described as an experienced nurse who has worked in multiple hospitals. By season 15, Alex is still not old enough to drive a car, though he should be at least 18 by this time, however, his age was referenced as fourteen in season 14 and fifteen in season 15.