Genetic Predisposition to Disorders

Thanks for your post.  My condolences to you for your multiple losses.  Research on the heredity of depression within families shows that some individuals are more likely to develop the illness than others. If you have a parent or sibling that has had major depression, you may be 1.5 to 3 times more likely to develop the condition than those who do not have a close relative with the condition. You would also have a higher chance of developing bipolar disorder.  Keep in mind, this is not a guarantee that you will develop the disorder.

Bipolar disorder has a strong genetic influence. Of those with bipolar disorder, approximately 50% of them have a parent with a history of clinical depression. When a mother or father has bipolar disorder, their child will have a 25% chance of developing some type of clinical depression. If both parents have bipolar disorder, the chance of their child also developing bipolar disorder is between 50% and 75%. Brothers and sisters of those with bipolar disorder may be 8 to 18 times more likely to develop bipolar disorder, and 2 to 10 times more likely to develop major depressive disorder than others with no such siblings.

Again, these figures are based on statistics that show people who have family members diagnosed with either disorder have a higher likelihood of developing it themselves.  It is not a guarantee.  It could be beneficial for you to seek therapy to process the feelings that might come up for you around fearing that you might "end up" like your parents.  Having a strong social network is one of the best things to help.  Good luck to you.