My fiancée has been divorced since May 2000. At that time his exwife and him were awarded shared custody. She was around the kids for a few months and then decided she did not want to be around them any more and she had not seen them until 2008 at a couple ball games? Now my fiancée just got served with papers stating she wants the kids from Sunday to Thursday? He has been raising the boys without their biological mother and now just wants to take them from him where he would only see them about 2 days out of the week. We are going to see a lawyer, however we were wondering if there was such a thing as abandonment. She has not called them, sent cards, birthday or christmas gifts in all this time.
Please let me know what kind of information there is out there to help us?

If you wanted to charge her with abandonment, the time to do that was BEFORE she decided that she wanted a relationship with her children.

They are HER children, and it's better late than never, for them to know the woman that gave birth to them.

Unless she is a danger to them, or herself, she has the God given right see, love, and help raise her own children.

If she is a legitimate danger, by all means, hire a good lawyer and fight to keep her away.

Abandoment varies by state in some states it is leaving them at walmart and walking off, not leaving them with the other parent.
And in many states, just not visiting, or not paying child support is not even grounds to take away the other parents rights.

So a lot will depend on your state. Also all of this time, he did not go back to court and change the custody agreement, so the court will look that she had joint cusody this entire time.

He needs to counter sue or file first if they had not filed, for full custody the judge may go back and give her joint custody again, ( leave it as it is in place) or change it either way.