See the article titled “Tennessee Stud,etc.” which was circulating here a couple of days ago. When Fred’s first wife’s brother was asked whether the marriage broke up because of Fred’s fooling around, he said that Fred “took advantage of opportunities,” or words to that effect.
His former’s wife’s brother implied something negative about Fred? Oh, the horror!
I am assuming you are referring to the following:
Commuting between movie locations and Washington took its toll on his marriage and in May 1981 Sarah filed her accusations of "cruel and inhuman treatment".
She withdrew the petition the following March, and according to her brother, the marriage improved for a while.
But Sarah renewed the proceedings in November 1984, this time citing "irreconcilable differences".
Asked if Thompson was unfaithful, her brother replied carefully: "He has said he 'takes opportunities' [with women]. I will tell you it wasn't physical cruelty and it wasn't mental."
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This seems like a pretty thin thread from which to hang your accusation that Fred Thompson's first marriage was broken up because of his infidelity. I would note that in neither divorce filing was infidelity cited.