Worried about the effect on my child

[TriedTooHard]

I am very upset about how my problems with uBPD sister may affect my young son.   Right now I'm feeling like a loser and a failure in family relationships, and its only a matter of time before my "tween" takes notice.  I spent a lot of time in therapy being reassured of my options, and how to strengthen my son's upbringing so he can handle whatever happens.  I am in the middle of a big change with her and her young son (my nephew), and no matter how much reassurance I got in therapy, I could really use some additional support here. 

I chose limited contact because I felt very sad about how I treated my sister when we were little kids.  She and one brother were favored and spoiled, while I and another brother were bullied and ignored.  My parents would sometimes physically abuse my brother and me, and purposely destroy our possessions, in front of the favored children.
When no one else was watching, and my sister wanted to play with me, I would in turn bully her.  Aunts and uncles had a hint of what was going on, but ridiculed all of us for being weird.  They only invited us to things when they needed an audience, and were very stingy with gifts and food. 

My sister has shown signs of uBPD.  She became disabled 10 years ago, became dependent on my parents, and handed over her child to my parents.  Because of my own guilt for how I treated her, and pity, and wanting to be a better aunt than my own aunts, I had low contact with them all for years, and have been generous with my nephew.  My nephew is my son's only cousin.  My son is also an only child, and I have felt sorry for my son for the lack of family ties.  The past few years, my nephew's behavior has become more troublesome.  He and my mother have been on outings with us where they've behaved very weirdly, brought a lot of negative attention to us, and even put my son and my son's friends at risk physically with my nephew's antics.  He has an ADHD diagnosis, but another mom with an ADHD child saw his behavior and said it has nothing to do with ADHD.   She also saw my mother's behavior and advised me to keep my distance.  She has been a good friend to me and this was the first time someone outside of my family had one to one contact with them, warned me, and wanted to remain my friend.  In the past, friends used to just fade away quietly.   

In the past few months, it also seems like my mother's and sister's pettiness and passive aggressiveness increased.  Or maybe I'm just getting too old and too sensitive.  I am very well practiced at grey rock - I have spent many times on the phone listening patiently to my sister complaining bitterly about my mother, or singing my mother's praises.  I don't agree or disagree, I ask her about her health challenges, and always tell her how sorry I am for her troubles.  I never rush her off the phone.  Last week, I was injured in an accident, and should recover, but it will be a long healing process.  My sister called to talk to me about it.  I was crying and stressed.  She sighed and hung up on me.  She emailed me a funny cartoon 2 days later.  I emailed back "go f*** yourself."  So much for grey rock.  I think this is it, not sure how we can all go back to the status quo now.

I would appreciate any advice on how to move forward with the few remaining years of my son's childhood, with very little extended family ties left.

[TriedTooHard]

update:  I hope I didn't turn anyone away by describing my past treatment of my uBPD sister as bullying.  After reading many other posts from members dealing with a uBPD family member, maybe what I did was a childish and ill informed reaction to her and my parents' symptoms. 

Some of the things I did were:  wouldn't play with her, wouldn't include her in my friendships, suspected her of making passes at my boyfriends, threw a tantrum for her taking all my money from my piggy bank, showed embarrassment at her attention seeking, showed panic and anger at her risk taking, blamed her for being the favorite.

[qcdlvl]

I'm not sure why you've gotten no replies, but FWIW to me your "bullying" doesn't sound over the top and there are strong mitigating factors.

He and my mother have been on outings with us where they've behaved very weirdly, brought a lot of negative attention to us, and even put my son and my son's friends at risk physically with my nephew's antics.

I strongly believe our son's safety should take precedence over any guilt over "lack of family ties" - no extended family is better than outright dangerous extended family. The fact that this  physically dangerous cousin is his only cousin is unfortunate but not your doing and does not make him less dangerous.

He has an ADHD diagnosis...

Which IMO is irrelevant - he is dangerous and, regardless of why he is dangerous, that does not change the fact that he is dangerous.

I would appreciate any advice on how to move forward with the few remaining years of my son's childhood, with very little extended family ties left.

My advice is to put safety first - if relatives are physically or psychologically dangerous, then I think you must take whatever measures are necessary to protect your son - boundaries, consequences, lowering contact, whatever it takes. This goes both for your nephew and your mother, who is clearly toxic from what you write about your childhood, as well as your sister.

[TriedTooHard]

thank you qcdlvl for your validation.  Today, my health is improving and I am feeling more confident in the way I've dealt with my uPD FOO members.  I have to admit, I had a sub-conscious hope that my efforts would lead to uPD healing.  I let things slip the past few months.  Because of guilt, I let my support group memberships lapse.  My success helped me and my FOC to heal, but it didn't change the uPDs in my FOO.  I may always need support for that.  I hope this helps others.