Yes. You generally will be entitled to the marital portion of the pension. Pension accruals from the date of the marriage until the date the action for divorce was commenced will be divided based upon a specific formula. This will require a Qualified Domestic Relations Order to be issued by the court before any such split can take place.
If you meet the NY residency requirements you may file in either NY or NJ. The benefit of filing in NY is that you can avoid court appearances if both you and your spouse can agree to an uncontested divorce. Feel free to contacts our offices for a free consultation. (800) 518-0211. www.uncontesteddivorceny.com.
If she has willingly executed the stipulation and her affidavit(s) consenting to the divorce then it would be difficult for her to challenge issues of the marriage at a later date. However, it is not unheard of for a party to reopen a case even after a settlement agreement has been executed. The best protection, as a general rule, would be to ensure that she executes the agreement under the guidance and advice of her own counsel - this way she cannot later claim that she had no idea what she...
A post-nuptial is essentially the same as as any other marital or pre-marital agreement. It defines separate property and outlines the who-gets-what in the event of the dissolution of the marriage. As long as it is drafted properly and the terms of the agreement are not against public policy most terms will be enforceable. That said, you cannot waive child support or the like in a marital agreement and the document must conform to DRL requirements.
Technically, the 2nd marriage is void. He will need to commence a proper divorce with his first wife. I would recommend, as odd as it may seem, that your brother obtain a new marriage license in connection with his second wife once this issue is resolved. Certainly seek legal counsel for further guidance.
This is a broad question that requires more specific information. That said, as a general rule New York State provides for the equitable distribution all marital property/assets. Typically pensions and retirement benefits will be divided based upon a formula that takes into account the duration of the marriage - that is, you will be entitled to 50% of the marital portion of his pension and he will be entitled to 50% of the marital portion of your pension (or the net difference).