-kin as "descendant of" is possible, if we are talking of Slavic-based surnames, also Jewish names formed similarly. We must find then a Jewish name
Boyka ~ Beyka ~Baika etc? Does it exist?
More probably, in historical English, -kin was a nickname ending, as one can present
Hopkin < Hop < Hob <
Robert or Tanakin, an absolutely obsolete form of
Anna.
Boy may be just a boy, an old Frisian name of similar spelling like English.