The priest/deacon who celebrates a Catholic wedding is the church's official witness at a Catholic wedding ceremony. You are required to have two additional witnesses.
The following is an extract from page 793 "Code of Canon Law Text and Commentary", Canon Law Society of America, Paulist Press, New York 1985. It is part of a commentary on Canon 1108:
"In addition to the official witness, two other witnesses are required. They must have the use of reason and be capable of comprehending what is happening in the exchange of consent. Although a minimum age is not mentioned, witnesses cannot be below the presumed age of reason. There appear to be few other restrictions on the witnesses... While the witnesses are usually lay persons, clergy and religious may act in this capacity. They need not be Catholic or even baptised, since their sole function is to attest to the fact that the marriage took place. The witnesses are not required by canon law to sign anything, although their names must be inscribed in the marriage register. In some civil jurisdictions they may be required to sign a civil register or marriage certificate."
Wedding photo on Unsplash
17 October 2019