Can anyone help me with an accurate English to Latin translation?

Hi,


My family motto is "Loyalty without defect", and was originally in Latin. However I have lost the original and now can only remember the English version.





I am aware, however, that Latin is quite complex. I would like to avoid using any of the auto translators as they just provide a word for word translation that does not really work in Latin. Is there a Latin Pro out there who can help?|||This motto is an old french one -Loyaut茅 sans tache |||Fides (or Fidelitas) sine vitio


or also


Fides (or Fidelitas) sine culpa|||Your last name isn't Mountbatten-Windsor is it? I can't imagine why someone would have a family motto unless they were royalty...