I take the article to be when siblings are healthy. I don't take the advice to pertain to harmful relationships.

People have a right and a duty to engage in behaviors that reduce or eliminate harm to themselves and their dependents. If the siblings are causing harm to said person and dependents, they have a right to distance themselves from siblings, to the point to cutting them out of their lives completely.

Blood relatives/relatives my marriage do not have a pass to act in harmful ways. Once you are an adult you get to choose with whom you will allow in your life. If you cave to family pressure to surround yourself with siblings/in-laws who cause harm, then that is your call, you have to take responsibility for your part in the corrosive dynamic.