Fortunately you can easily change it. If you go to https://appleid.apple.com and login using their account details, in the Password and Security section, you can change the year of their birth. 1/1/2001 works fine, I think the key is that they need to be over 13 to change from Adult to Child account.
Benjy Fenwick (d. 1981) was a wizard and member of the original Order of the Phoenix. He fought in the First Wizarding War and was murdered and mutilated by Death Eaters before the war's end.
Fen is the son of Lauren Fenmore and Michael Baldwin. Fen was born prematurely and remained in the hospital for a while. Shortly after, his mother's nemesis, Sheila Carter, came to town with her face surgically altered to look like Phyllis Summers. Sheila kidnapped Fen, Phyllis and Phyllis' baby girl, Summer Newman.