The divorce between Lucinda and John.
No reason has ever been given for their divorce. However, if he was the sole wage earner, as I believe he was at the time,and there was no serious animosity between the divorcing couple, it was not that unusual for the higher wage earner to help the stay at home spouse choose their attorneys and pay both sets of fees.
As low key as Lucinda has always been, I expect they parted on good terms and likely had already worked out the property division, child support, child custody, and other asset division. If they were not fighting, which I have never thought they did, then he likely paid for the divorce attorneys because it was not a financial hardship for him to do so and it was a HUGE goodwill gesture on his part as the spouse who wanted the divorce.
As far as I know, they've always been cordial. I've read all the books published on JBR's murder, and Lucinda was kind and supportive, but very quiet and declined interviews and the like. The total opposite of Patsy, she is a true Southern lady.