Are Carl and Fiona related?
Fiona is not Carl Gallagher's mother, although she did raise them for most of the series. When Shameless Season 1 began in 2011, Carl was nine years old, and Fiona was 21. So, the eldest Gallagher child was 12 years old when her sibling was born. She was not in high school yet, so the fan video is inaccurate.