Earlier today, it was revealed that 9-year-old Lily Harvey had been contracted for a role as a 'cheeky youngster' on the Walford show.
Kirkwood told PA that the decision was taken to hire Lily Harvey on the strength of her audition tape, prior to any relationship between the actresses being known.
He explained: "The truth of it is I didn't know she was Lacey's sister until after I said she was the girl I wanted to cast.
"I sat down and watched a tape of a very talented young girl and it was only after we decided to cast Lily that I was told it was Lacey's sister.
"Lily got the role entirely on her own merits."
Lily Harvey begins filming in January as Shenice, the daughter of Kat Moon's friend Martine.