Assigning a value based on how often that entry occurs

We are needing the Fee column to be auto populated as follows i.e. the First child in the family gets charged Fee1, 2nd Fee2 etc up until Fee5 (Which is the lowest fee possible). What formula can I use to create this?

https://techcommunity.microsoft.com/t5/excel/calculating-values-based-on-position-in-family/m-p/3599505#M158860

Example: Annual Invoicing Workings(families).xlsx