Hello,Welcome to Just Answer and thanks for your question. I am assuming your Johan(n) Schusler was the one in the convalescent home in Pegwell in 1901. If that is the one, he is also in the 1891 census. His death is registered in the 4th quarter of 1901 in Hackney, London. His full name was John (i.e. Johann in German) Matthew Schusler.
1891 CENSUS -XXXXX Hackney, South Hackney, London
I don't see Johann in the 1881 census, but his wife and daughters are here:
1881 Census -XXXXX Hackney, South Hackney, London
I did not find them in the 1871 census, although they may have been in England since their eldest daughter was born in Middlesex/Londonshire in 1872.
Without knowing where they came from in Germany and finding the parents, there really isn't a good way to tell if he had siblings or if others came with him and Madeline. You may want to check published passenger lists for entries into England around 1870-1872 to see if you can find them. Some lists included home addresses while others just had the country they were coming from. There may also be emigration records from Germany but those aren't online either.
If this is the same family, daughter Frances Paulina married Edwin James Gooch in 1896 and daughter Annie Catherine married Athelstane John Kent in 1900.
1911 Census -XXXXX Hackney, South Hackney, London
There are a lot of records for Baden, Germany. (Baden Baden is a tiny spa town in Germany). It could take you weeks to read all the births, and without knowing his parents' names you wouldn't know any more than you did before you started. You would, however, have tired eyes and a sore bottom.
Checking incoming passenger lists for about 1870-1872 is more of a managable task and more likely to yield his birthplace.