Is the brother required to divorce his wife because his brother divorced her sister, and is he considered disobedient to his parents if he insists on going through with the marriage to her?

The questioner is not obligated to divorce his wife because his brother divorced his wife, as there is no connection between the two contracts. The father's belief that the relationship will be difficult is not binding and does not necessitate divorce. Not divorcing the wife is not considered disobedience to the parents. The phrase "circumstances did not will it" is incorrect; the correct phrasing is "Allah did not will it."