http://mobile.nytimes.com/2016/08/06...lies-late.html
Lots of 50-somethings having kids late, careers + reproductive technologies will make this more common in the future.
Yes you are out of line, two underage children with a 50k a year income is right about the national average. If you're over 18, move out and get a job, if you haven't done so already.
Not your life, you sound petty and bitter. Be happy for your mother and stop being so resentful for a decision that is really none of.your business.