Andrea, Polly has found their marriage, but before you rush off spending money on certificates, try working back through the census records. In 1891 and 1881 they should be with parents and any brothers and sisters. I presume you have access to census records as you found 1911. If not, try around your local libraries or family history centres for free access to Ancestry or FindMyPast. Using Census records and the FreeBMD site that Polly mentioned, you should be able to work back to early 1800's. Peter in Sydney