When you decide to get married, you're not just marrying your spouse. In fact, there's an old saying that states, "You're not just marrying your spouse, you're marrying their family." That's a saying for a good reason. When you marry someone, his or her family is part of the package. It's rare that a person would walk away from family for a spouse or cut off his or her family as a result of disagreements.
While you're becoming part of a family when you get married, you could also lose family during a divorce. When you divorce, it's normal for the blood family of the spouse to stop seeing or talking to the ex-spouse. This has the potential to be emotionally damaging to people for several reasons.
First, when you marry into a family, you start building relationships. If you have children, they see both your family and your spouse's family. During a divorce, those relationships are strained, which could make it harder to spend time together or to see each other's relatives freely. Next, people may feel that they have no choice but to cut off the ex-spouse, believing it would be disloyal to continue talking to him or her when the blood relative is hurting or has decided to move on.
It's important for everyone in this kind of a situation to take time to grieve. There are some relationships that may end, but after some time, it may be possible to rekindle them. If you have children, it's vital to make an effort to include your ex's family in his or her life unless there is a reason, like abuse, that it's unsafe.
Source: Family Kind, "Separation, Divorce and the Extended Family," Dana Greco, Don Desroches, accessed Feb. 20, 2018