Premise: Albert V of Saxe-Lauenburg (mid 1330s – 1370) was the second son of Duke Albert IV of Saxe-Lauenburg and Beata of Schwerin (*?–before 1341*), daughter of Gunzelin VI, Count of Schwerin. Albert succeeded his elder brother John III in 1356 as Duke of Saxe-Bergedorf-Mölln, a branch duchy of Saxe-Lauenburg. He died without an heir and was succeeded by his younger brother Eric III.
Hypothesis: Albert's brother was John III.