I don't have a good relationship with my family. Will mending the relationship help my depression?

Family is important. Depression can be difficult to handle, and social support (friends and family) are crucial part sof a comprehensive plan. Also, if you feel the family dynamics are a source of your depression, mending that makes sense as well. Good luck.
See below. If you feel that family relationship is a part of your problem, look at what's causing strain. The thing to remember, we cannot change somebody else (e.g. Family members), we can only change how we cope with the family. Find a counselor who can help you through that process figuring out where to go with your family relationship and how all of the above affects your depression.
Probably. There are many causes of depression. Family stress/distress is one such cause. If you believe your have issues surrounding your relationship with your family, mend the fences. You may need counselling and family therapy to overcome some of the issues. It may be helpful to your and to members of your family as well. There are others as well to consider. Best to you!