Stella Ianna Princess Gallagher was born at the end of Series 5. Frank stated that he did not name her after the beer Stella Artois, but because she is "a little star". Her middle name is Ianna, as a thank you to her half brother, Ian, who helped deliver her, and also as Frank's way of apologising to Ian for yet another row over his parentage.
In Episode 1 of Series 6, she appears to communicate with her parents telepathically and even narrated the episode, though this is likely a drug induced hallucination on their part or a half serious idea on the part of the writers. She was voiced in that episode by Kelly Condron.
Since her birth in Series 5, Stella has been cared for mainly by Debbie, Liam, Carl, Libby and Patty, in the absence of either of her parents, as per custom in the Gallagher family. By Series 11, all Stella's main care givers were gone so she is most likely being cared for by Aidan, Marty and Kelly.
As of Series 11, Stella appears to be growing up fast, being able to cover for her father when police came to arrest him for taking part in a riot.
Unlike her other eight siblings, Stella is being brought up without a big family around her. She is yet to meet her sisters, Fiona and Delia and her brothers, Lip and Nigel. However, she is seen regulary with Aidan Croker. She pesumably has no memory of her other siblings, Debbie and Ian, as they left when she was only a baby.
Like her siblings, Fiona, Debbie, Liam and Carl, Stella has taken control of the Gallagher household at a very younge age, becoming a skivvy for her father and surrogate brother, Aiden. She is becoming more assertive, as she performs a number of chores, and even plays pranks on her father and Aidan by shaking up their lagers before giving it to them.
Stella finally meets her older brother Lip in Episode 11.8, as well as her niece Katie (who's also three years her senior). Katie and Stella form a bond with one another, to the point where a concerned Katie was reluctant to leave her six year old auntie on her own when Mimi came to take her away from the Gallagher house.
Stella becomes an older sister for the first time to new Gallagher sibling, Ben, in the final episode of Shameless, Episode 1114. Stella begins to deal with the stress of looking after a baby, with both of her incompetent parents present. Fortunately, Monica's reaction to losing baby Ben's twin in the womb was to contact the rest of the family. Fiona came, thinking Monica had a miscarriage. But realising the true situation at the Gallagher home, she becomes determined to help her two youngest siblings escape the life they're doomed to endure in Frank and Monica's care. Despite being left with Kev Ball by Fiona temporarily, Stella decides to walk out with her brother in her arms and find her father. But she finds Frank in the street, after his spat with Monica, where he claims to blame Stella, as well as all his kids, for ruining his life, and tells her that he's leaving. Afterwards, though, Frank finds Stella and Ben outside a park, and tries to apologise for his earlier words.