So here's the two census records you found, put together:
1930 US Census San Francisco, San Francisco, California, USA Carl B. Johnson 39, born about 1891 in Sweden Wilhelmenia M. Johnson 22 in Norway [see correction in 1940 for age and birth place] Margaret M Thomson 39
1940 US Census San Francisco, San Francisco, California, USA 1954 18th Street Carl Johnson 48 born about 1892 in Sweden, painter, proprietor Wilhelmina Johnson 41 born about 1899 in Australia, wife Margaret Thomson 47 b abt 1893 in Australia, single, sister-in-law, clerk, office, dry goods company **All three of them resided in 1935 in Same House (a question on the 1940 US Census) **Wilhelmina was the person who answered the questions on this census. **All three of them are listed as aliens.
Since there are no children in the 1930 or 1940 census, we can presume that there are likely no descendants to be found for Wilhelmina or Margaret.
About Stanley - I wondered about him too. A matter to be looked into...
Sonia, do you have records of the siblings there in Australia (children of Thomas Thompson) other than your great-grandmother Adelaide? Who did Adelaide marry? Perhaps she traveled to USA to visit as well....?