Your situation is not an easy one and I agree with the majority that it would not be beneficial for you or your family (in the long run) to try and get reinstated.
Re: your question as to having your baptism declared invalid.
When I was an elder, I personally dealt with a woman who, at the time was in her 40’s and had not been a JW for 30 years. She never really believed the WTS doctrine . She was baptized (the act that makes the elders have jurisdiction over you) when she was 14 years old because her friends were getting baptized at a summer convention of JW’s. She was disfellowshipped as a teenager for an act of premarital sex. She was later married and had a family and tried to live as a Christian. None of that mattered. She was prevented from having a normal relationship with her mother. The reason for her inquiry to the elders was that she wanted to have her baptism declared annulled because according to her it was not genuine. With this organizational declaration, she would no longer be viewed as disfellowshipped and she would be free to have a relationship with her mother. After writing the WTS in Brooklyn, NY, I received instruction on what to advise the woman. It was decided (on what basis I still do not know) that her baptism was considered valid and she was still to be viewed as disfellowshipped. The religious authority ruled and had spoken – from Brooklyn, New York and having never met this woman. After informing this woman of the decision not to grant her request, she broke down and cried. I will never forget the effect this had on this woman. This was her mother. She essentially lost her mother. This was not a wicked woman. She was even willing to meet with an ecclesiastical authority that she did not even recognize in hopes of having her mother associate with her. There never was any question in her mind that unless the elders or WTS approved her request, her mother would not have association with her. What a tragedy that I can only hope God will forgive me for participating in this and not speaking up for what was right and just. I do not think that a persons' baptism can be declared invalid by the organization, so this probably is not an option for you.
I think that if you continue to show them love and support that is the right thing to do and hopefully in time you will be able to have a relationship with your siblings. Someday thay too may begin to doubt the religion and you will be in a position to help them.
