When you choose a guardian for your children in your online will, you’re choosing who will look after them if both you and their other parent die before they turn 18. A guardian for a pet is a similar thing, but with pets (who can’t come of age, and don’t have other ‘parents’ - at least, officially speaking), you are choosing a guardian for as long as your pet survives. Guardians can also be executors and beneficiaries.