Musar к Берешит 2:21

This explains how the same Moses who was reported to have refused to suckle on the breast of a non Jewish wet nurse (Sotah 12), could nonetheless marry a woman of non Jewish origin (because she was to him like Eve had been to Adam, i.e. a missing part of his body, see Genesis 2, 21-23). When Yitro came to Moses in the desert, he said to him; "come forth on account of your wife whom I give to you, and her two sons." The first letters in the verse אני חותנך יתרו (Exodus 18,6) spell אחי, my brother. This was when he had realised that he, Yitro, representing Cain, was Moses' brother, whose former incarnation had been Abel.