You can get a new birth certificate in certain circumstances. However, I don't think Kevin could in this case.
Firstly under the rule that says, "If the parents were not married at the birth registration, and the father did not attend the registration process, it is possible to amend the birth certificate. It can be altered to show the fathers details and the child's surname can also be altered. Please note that both parents must agree to such a change." The last sentence would seem to rule out the possibility of changing the birth certificate in this particular case.
Secondly, under the rule which says, "A registration of a birth is a historic record and so is intended to record the facts as they were at the time at which the registration took place. However, if it is found that an error was made at the original registration, changes are possible. Applications for corrections should be made by the person who first registered the birth and at the same Register Office. Depending on the circumstances, documentary evidence may be required. This should show that the child is being brought up in a different name to the one on the register and from the earliest date possible. This could be in the form of an NHS letter, a bank statement or a medical card." But again, it would need Molly to make the alteration if she was the person who registered the birth. I can't remember, but I guess it was Tyrone who actually registered the birth however, so it would need him to make the change.