If disaster should befall the larger chick the parent can switch to feeding the youngest and it will exhibit a constant growth curve from the day of active feeding. From Wikipedia
Simply send them a letter (with proof of delivery) using the contact information found on your credit report. Generally they have 30 days to investigate and get back to you, or the information must be removed.
If you are in the UK they will drop off after 6 years. Your credit report is like a 6 year rolling thing, though, so the debt amount may continue to report to your credit file until it is paid off, and will then show for a further 6 years after that.