How do I know if I have traits of BPD or if it is just PTSD and codependency?
How is it possible that I could be the only one of my family that does not have a personality disorder? None of them have been diagnosed, but my mom definitely has the traits of BPD and my dad fits the bill for NPD. My oldest sister definitely is BPD, she even once faked having three personalities. My brother has many traits of NPD and my other sister is most definitely BPD with a lot of traits of PTSD. She also received the brunt of the physical abuse by our mother.
I felt these two kind of went together so I thought I'd answer them together. I would think a therapist would be able to help you answer those. But disorders like BPD seem to run on a wide spectrum, so no two people are going to exhibit the same symptoms and some will be worse than others. You may have only picked up some of the behaviors (fleas) but aren't enough to be considered having any disorder. I know that I picked up some fleas and I've been working very hard to get rid of them.
How can my parents be married for so many years and yet I and two of my siblings can't maintain a relationship?
My parents have also been married for a very long time (getting close to 50 years), my mom is uBPD and my dad is an enabler. In their case, I really have a feeling that my dad's mom had some PD (talked about how she was dying for years, expected her husband to cater to her, favored my uncle who was in jail over my dad who was the model son, etc) so I think he's repeating the cycle. He thinks their relationship is normal because that is all he's ever known. Plus, my parents are what you would call "old fashioned" meaning that they don't particularly believe in divorce. I do know my mom has threatened divorce multiple times, but when I've suggested if she's so unhappy in their marriage that she should leave, she goes all waif and wails that she'd have to find a job and that she "worked hard to make my dad the man he is" so he owes her for all her years of hard work. So while your parents may still be married, it's probably not a healthy relationship and neither is willing to end it.
How can I know if I have reached a level of emotionally maturity and stability to have a healthy relationship?
I don't know if I have a good answer to this. It sounds like you are on your way though if you are starting to see the red flags. Maybe after you are able to deal with the guilt you are feeling. I think it's hard as kids not to attract unhealthy people. I was also in a very serious relationship with an emotional abuser (we were engaged), but we didn't end up going through with it. My current husband isn't an abuser, but he does have his share of emotional issues (as do I). But despite each having issues, I don't feel our marriage is unhealthy - we balance each other in positive ways.
Also, I have been accused by one sister of having buried rage. Really? I don't have tantrums. I don't scream and yell at people. I didn't take a shot gun and blow out a window, like she did when she was angry at her first husband. Am I missing something? Could I have buried rage? How do I know if I do have buried rage when I don't feel angry all the time? Should I feel angry all the time if I do have buried rage? Is she just projecting?
Obviously I don't know you well enough to say one way or another. It's definitely possible she is projecting her own anger issues on you. It's also possible you're burying them. Most of my personal issues lie with my inability to appropriately express emotions and I realized that I had anger issues too. I realized that I was holding my anger and frustration in so much that eventually I'd hit a breaking point and just explode. That was the hardest for me to admit to. Whether you have anger/rage issues is something only you can answer by taking a hard and honest look at yourself.
I know it's long, I hope I helped.