It could be of the same origin, very often a S was added to names. Sometimes because of a simple explanation. When mentionning someone f.e. M.Alf is coming to the registration office to register a child-nowadyas the mistakes are very small and can be corrected- a hundred and more years ago when a child was registered it was more difficult to correct a misspelling sometimes even impossible, but very often it was written the way it sounded and the person registring a child did not read and then a child's name could be written down as Alf's child, becoming ALFS. This is a possible explanation, I won't say that it is of the same origin, since there are two branches (or more) one from Germany the Eifel region and the other a possible scandinavian origin. The first one from the name of a kings court ALFF and the second one from the first name Alf (sometimes short versions as well from Alphonse or Alfred)
Hope that this is of some help to you
Ps you can always send me some more information from the Alfs part in your tree.