I'm confused by paragraph 3; please re-phrase in layman terms. I'm advising my little sister to enter into a separation agreement and file it with the court or the clerk to protect herself and her small children. Her spouse has been having an affair recently and now wants to separate. Would the agreement have an adverse effect if divorce occurs? What's the difference is it's no fault or adultery?

If you are not a lawyer, I would watch out in dispensing legal advice even if it is your own sister.

As to the effect of adultery on a divorce, we are such a gross and vulgar society that no one cares who committed adultery or who did not. So in practical terms, it does not matter whether you file a divorce grounded in adultery or one grounded in no fault, Remember that the law in New York changed in October, 2010. New York now has a no fault provision. So you do not need a separation agreement to serve as a basis for a ground for divorce in New York just as you do not need to allege and prove adultery.

Where an adultery allegation may have some weight is if that fault was "egregious". That could result in a bigger financial win in divorce court, but the chances of proving how an affair was egregious are quite slim.

Lastly, the court will protect the child no matter the level of fault.