Why does marraige record show both parties having the same last name?
My relative, Emma Klinger (21) married Wilhelm Klinger (28) in 1906. https://www.familysearch.org/ark:/61903/3:1:S3HT-6SLW-911?i=219&cc=2466357&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AQKJ4-KN5S I find this very odd. Is this because the Klinger name was very common in Poland or because they were related but not that closely?
If that isn't strange enough, Emma L. Klinger (17) married William E. Klinger (17) in 1898. https://www.familysearch.org/ark:/61903/3:1:33SQ-G58D-Q5TD?cc=1589502&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3AVFMH-TGM
Is there some long lost rules about marrying your relative that has changed from todays rules? Is this common or rare in genealogy records?