To be marrying in 1900, let's imagine the person is 'of full age' i.e. 21+ for legal purposes, and did not need parental permission. that means a birth date of around 1879, when the parents of this person registered the baby's birth, they would have probably only asked for the free short certificate, which was a very basic format and waqs more proof that the parent/parents had followed the law, it had only become a finable offence to not register a few years earlier. before that the onus was on the registrara to register known births. Therefore i would say that as a short certificate just had the name of a person, and no parents name, that was not exactly hard to misuse, what was more important was a baptism certificate, though obviously more for church weddings. i have two elopements in my paternal side and both used false parents names, they were brothers marrying 5 years apart but using the same church in farnworth near widnes, where it was known the incumbant would turn a blind eye . What i am rying to suggest is that anything was possible.