English HRC: What if you don't know the romanized name of a parent?

When applying for an English household registration certificate, what happens if you don’t know and have no way of finding the English romanization name of a parent? In my case, my wife’s mom died when she was a baby and nobody has any idea, or any documentation about what her romanized English name was. Its possible she never had one, and if this is the case, can we create our own translation for the sake of the household registration document?

yes, but it should be the standard translation basically.

Operation Directions for Issuing Household Registration English Transcript

(3). If the applicant is unable to submit the passport of ROC or other documents recording the English name, the applicant may follow the Guidelines of Using Chinese Phonetic Spelling and fill in the application form (Shown as annex 1) by himself/herself.