chrismb on Family Tree Circles

I have been trying for several years to trace my great grandfather with no success. His name was Kristian/Christian Martin Petersen/Peterson. As the name is very common I have followed several leads but they have proved incorrect.What I have found so far is:
According to his marriage certificate he was born in Christiana, Norway around 1877.His parents names where Peter Petersen and Annie Oleson. When or how he came to Australia is unknown.
He married Grace Pomery in 1907, and they had two legitimate children. Family history says he returned to Germany during world war one and that he and Grace seperated several times due to the stigma of his accent. He also made trips to the USA and it was during one of these trips that Grace fell pregnant to another man. I have the divorce documents and a letter in which she explains to him what happened. They divorced in 1913. He gained custody of the two children named Christian and Thelma, and the third child must have gone with Grace, her name was Coral. Thelma died aged 19 and my grandfather died aged around 80. But he never spoke of his mother or father. Until recently we did not know why until I discovered he had been put into the Randwick Asylum for destitute boys by Grace, and left there for around a year until his father picked him up.
They only other leads i have is that he requested a decree nisi so he could remarry in 1925,but i can find no record of the marriage, and that my mother recieved a postcard from him that came from new zealand.
If anyone can give me some idea where to go next any help would be appreciated

I am seeking information on John Bailey Brotherton Born 1875 Died in Dubbo in 1962. He married my great grandmother Grace Alma Petersen,who died in Dubbo in 1954. I am seeking any relatives that may be able to give me information on them and their life together