That's why Step-parents should not be overly involved with their step children!
I was just informed that my ex-husband split with his second wife. He was with her for about 10 years (wasn't married the whole time, I do not remember when they actually got married) and have 8-year-old son together.
My daughter's step-mom is OK woman but was never overly involved or interested in my daughter. Now I am very glad she wasn't because my daughter would be too upset. (It goes with the topic how much step-parents should be involved with step-kids? As little as possible because they can be gone any time and kids get hurt second time around!) My daughter is rather upset about her little brother who would most likely stay with his mom because my ex is on business trips a lot.
The other thing is that last couple of years my ex did not pay much child support (not like he ever paid that much to begin with) because we had an agreement (proposed by him) that he will pay our daughter's tuition and cost of living for 3 years of college, which is a big amount of money.
Now on her first semester of college he tells her that starting next year he can't pay as much because he needs to pay child support to his son and needs to get himself a place to live.
Well, things happen, but my ex-husband did not pay child support lately at all because he was saving for her college! I was not getting child support but my kid's college won't be paid either!
In any case men just do what they want to do, but women pay for it! He left every woman he was with! Well i actually left him, but only because he made life unbearable for me.