Eventually, slavers raided Great Lanta and Monica was separated from Ehren. She went from slave master to slave master, never giving up hope that she would see her son again. Eventually, she found her son, but as a slave owner himself. He blamed her for the childhood he had lost to the slavers, and beat her daily. Yet, no matter how hard he beat her, she would simply smile and say "I forgive you". This ate away at Ehren, until one day when he realized the errors of his ways and freed all of the slaves he owned.
However, there is nothing concrete about Saint Monica's story, so it's possible Ehren is a fabrication thought up by Father Clifford.
Ehren is only mentioned in Fallout 3.