This happens in California.
I met my wife in 2007 and she had 2 kids. They are now 17 and 9. The father of the kids does not work and has not worked in years. He recently moved in with his girlfriend because they had a baby. His girlfriend supports him now ( as my wife did before her ) and supports the kids when they are at their home. My wife has joint custody with the kids bio. Last year he asked his son to come and live with him ( he was no present in the kids life for about 2 years) and he now spends more time with his dad then with us. (about 80 / 20). He has no source of income what so ever, and is now requesting for child support, although we spend WAY more on both kids then he does and have all the receipts from the past 5 years to prove it. I am the stepfather and I love the kids as my own, but my relationship with the kids bio is terrible. He is a classic (and diagnosed) case of bipolar disorder and a sociopath. ( too many stories about how he has tried to affect my family )
- My question is - is there a chance I might have to pay child support for his 17 year old kid that is living at his house longer than ours,when we already pay for way more expenses than the father does? Or is he just playing another one of his games..
- Also the child turns 18 in June.. Does child support go beyond 18 years old..

What does the child support order say? Minimally it will have to be reviewed due to changed circumstances. Obviously the sooner your wife files for review, the faster the situation will be resolved.

Orange County (and I don't know where you are) says: "The legal duty of support continues until the child turns 18 years of age, and has graduated from high school; or turns 19 years old, whichever occurs first; marries; dies; or is legally free in some way, such as joining the military UNLESS the child suffers from a disability." Superior Court of California - County of Orange (http://www.occourts.org/directory/family/child-support.html)

This is a very good site when it comes to child support in California.

Judy answered the question of age. But one of the main factors of support is the time spent with the parent.

There is a chance your wife (not you) may have to pay support if he applies for it. Personally I don't think it likely, but stranger things have happened.

Thank you for your answer. He has not yet filed for child support. This is in San Diego County.
I'm looking for more information on what the chances are of him getting any child support under our circumstances, if he does file.

Currently we have joint custody of the kids and should be paying 50 / 50 of all kid related expenses. We already pay way more than he does on everything that is related to kids (school, heath, clothing, entertainment.. ) He never followed the divorce contract making his own rules along the way. The father lives in his girlfriend's apartment and claims that he cannot get a job because he needs to stay home with his new baby. So he is asking for child support to pay for his older son that moved in last year.

- I know he can ask, but does he have any chances of getting child support since we have proof of already taking in at least 80 % of all the expenses related to the kids? (maybe more) Also, Can he get any child support now even if he didn't care financially for he's kids for 2 years and still hardly does.. Will this carry any weight on the court decision?

- I'm I, the stepfather, responsible? And can he ask me to pay child support for his kids, if their mother also does not work and has no income?

No one can predict what a judge will do. Family Court judges generally have a lot of leeway. And the actual law doesn't give you much hope. While on the face of it, justice would say that you shouldn't have to pay we can't tell you what will happen in court.

While its not unknown that a step father will be held responsible for support, its not common.

Did you look at the site I researched and posted, particularly the section titled "How does the court decide how much the child support amount should be?"

@ Judy
Yes, I specifically enjoyed reading the part about "Earned Capacity". It's time the kids father got to work to help support his kids, instead of relying on the stepfather and his girlfriend to do it. Not sure... but I think (hope) any court would see that the father does not work by choice, not by any other reason. And with 3 kids to support asking for child support when you should be working to support just does not seem fair... My wife and mother of the kids also does not work, so he would need to come after me... I guess...

@Scott
Thanks!