Adolf Ols.(20y), Anna Ols.(24y), Adolf Ols.(1m)

Adolf Ols., age 20, Anna Ols., age 24 and Adolf Ols., age 1 month are all listed emigrating in 1887. They are sequentially listed with a residence of Vigten. The older Adolf Ols. and Anna Ols. are both listed as unmarried. The younger Adolf Ols. is listed as "Søn". May I assume the younger Adolf is the son of the older Adolf and Anna Ols. even though each is listed as unmarried? Also, is it common for an unmarried women to take the surname of the father of her child? When searching the Archive for 1887 emigration records from Vigten, with no names provided, is it common for family members to be listed one after the other? The reason I ask is Adolf, Anna and Adolf Ols. are listed immediately after the Anton Rønne family. The registration dates are all the same, 20.4.1887. The destinations are all the same, Emerson, Manitoba. The ship names are all the same, Hero as well as the ship line, Inman. I am trying to discover if "Anna Ols." is Anton Rønne's eldest daughter, Anna Ludvika. Many thanks, Tmlynch