Keep calm and maintain your composure in all interactions between your husband and brother. Try to stay calm when your loved ones can't agree, says professor and researcher Preston Yi in a 2013 article in "Psychology Today." If you don't immediately react, you can think more clearly and make consciously correct choices in handling the situation. Keep your statements neutral and maintain a calm tone. Avoid taking sides or getting involved when your husband and brother are disagreeing. If you see them becoming agitated, ask them to lower their tone or take a time out.

Schedule a time for your brother and husband to sit down and attempt to mend their differences. Offer to serve as a mediator during the conversation. Allow them to take turns discussing the issues that they disagree on. Give each one an equal opportunity to share his perspective. Encourage them to focus on talking about the problem and avoid making generalizations or "global" statements about the other person. Ask them to discuss what they need from the other person to move past their conflict.

Ask your husband to be civil when he is around your brother. Brainstorm ways in which your husband can avoid being engaged in conflict when he is around his brother-in-law. Recommend that he avoid topics that often lead to arguments. Help your husband find things that he has in common with your brother, such as a love for football or a shared hobby that they can talk about when together. Commend your husband for his effort when he is friendly to your brother.

Accept that your husband might never get along with your brother. Push aside your dreams of a husband and brother who play golf and barbeque together. Pressuring them to spend time together or making them feel as if they have to become good friends will only strain their relationship even more. Allow them to be cordial but still keep their distance. Plan ahead so that their encounters occur in neutral and pleasant settings so that they are more likely to get along.