What impact does bipolar disorder have on relationships family members?

For this question it depends on each family and on the patient themselves. I suggest finding and talking to people with bipolar disorder and hear their experiences.

Sorry if there’s a specific answer you’re looking for, but from personal experience the manic or hypomanic and depressive phases can last for short periods of time to long periods of time, and the mood cycling can cause stress or confusion with family. Hypomania is a less intense version of mania, but they still have serious effects. During those phases people can be driven to do wild things, be more confident, and feel a lack of need for sleep among other things, and seeing someone act that way can damage relationships, especially with the irritability mania or hypomania can cause. During a depressive phase irritability and anger can also happen, and thoughts of suicide, indifference toward people/things, lack of energy, and feelings of worthlessness. I don’t know what perspective you want this from, but being bipolar myself and having family members who are bipolar, i’ll talk about both. Seeing someone you care about go through one of the phases can certainly create distance and damage relationships because of the mood swings and potential anger toward you. And going through it myself I’ve found that I stop caring about family, and how my actions would affect them. The back and forth is hard to go through and hard to see someone go through and it causes sadness all around.
That got long lol sorry. Hope that was at least somewhat close to the answer you want :)