I am a father currently living in GA and my kids are living in MD with my ex wife. I'm trying to figure out if I am wrong for having a problem with my ex leaving my 2 children 8 and 9 with her niece who just turned 17, for five days? She went on a business trip for the five days and didn't even mention to me she was going (found out when I called my kids and they told me.) When I spoke with her she was defensive and threw my situation in my face. I was laid off from my job over a year ago so things are very tight for me right now. However, she did just receive my tax money, $9,800. So my issue is why not fly them down to me and have them stay with their father instead of with a child and have us both hundreds of miles away if something goes wrong. She says its legal and not a big deal because its her family. Am I wrong?

In my opinion, it depends on what the 17 year old is like. In high school I had a friend who babysat for this family. Whenever the parents wanted to get away, they left the kids with her.. so it was pretty normal for my friend to stay the weekend or longer at their house watching the kids while the parents were away. My friend had proved she was responsible and could handle the children though.
But that was something that both parents had agreed to also. If you're really not OK with her niece watching them, once you've calmed down, when you're not angry, or upset, or feeling too emotional about it, call her and calmly talk it out. As far as I know, it's not illegal (someone please correct if I'm wrong.) and maybe to her its not a big deal (does her niece have other family members she could call in the area in case of an emergency? Would she have been able to get a hold of you or your ex wife?) but if you're not comfortable with it you should talk to her. And remind her that you're there and would be more than willing to take the kids if it came up in the future.

Hey,my eldest at 17 was very responisibly and mature for her age,and could be trusted with my 8 year old for a day,if I was going overnight I asked my mother,only I was more comfortable with that arrangement,not that my eldest could not care for her,my second has just turned 17 and I could not trust to care for a head of cabbage let alone a child.

If the 17 year old in question was able to reach another adult if she needed,I can see why your ex would be OK with that.

Thing is,if things are not good between you,maybe she just did'nt even think to ask you.

I agree with justcurious in that you need to let her know you would be available in future.