When Frank is telling Steve about his wife having left, he says that Fiona was 14, Lip was 11, Ian was 10, Debbie was 7, Carl was 5 and Liam was 4 months old. Earlier in the episode, they said that Carl was almost 9, which would only make Fiona 18, Lip 15, Ian 14, Debbie 11, and Liam 4, but Liam appears to be a toddler much younger than 4. Though her age is not stated, given the show's timeline, Fiona should actually be 20, meaning Liam should actually be 6, definitely not sleeping in a crib or wearing diapers.
However, frank was drunk and high when he said this and barely knows anything about his kids anyway, so of course he would got it wrong.
However, frank was drunk and high when he said this and barely knows anything about his kids anyway, so of course he would got it wrong.