Do you work? What are your finances like? Are you able to separate finances as part of agreeing to stay, and ask him to give you X amount each month to cover the bills and needs for your kids and let him use what's left for the other kids?  

Have you sat down and done a budget and showed him how much you have, how much his going out, and how in debt you are? If you've done all of that and he still shrugs his shoulders and hands over extra money to BM, then I don't know what else you can do.

If he thinks the drain on his wallet will stop at 18, he's lost his mind. There is college tuition and books, car payments, etc. 

"I believe in marriage for life."

This is not life. This is purgatory to support someone else's life.

This is not a marriage. This is purgatory to support a previous marriage.

Your DH, skids, and the ex by extension of what DH does are all using you to support the first family and not allowing you to have your own family.

I know exactly how you feel, been there.  Divorce settlements regarding CS in my country (UK) are made generally between his and hers lawyers, but DH insisted on giving grasping, greedy NPD BM far far over the odds in CS than he needed to.  And all through their growing up he continued to foot bills he didn't need to pay. Teens in this country, (UK) normally never get cars bought for them or insurance paid for, and if they want to go to higher education they get a student loan, parents are not expected to pay. However, guess who ended up forking out over £60k for SD24's first degree so the poor ickle diddums didn't have a nasty student loan to pay back?   since then she has also done a Masters degree (student loan) and a drama course of all things (£12K) - I insisted DH didn't pay for that one - apparently step father paid, more fool him, huh? 

The gravy train has now well and truly hit the buffers, and SD24 is squawking all over the shop about having to pay her own way. Like your SKIDs, mine were raised to be lazy, irresponsible leeches.  More by luck than judgement, SD22 has actually been holding down full time employment for the last 2 yrs but I imagine her sister will still be sticking her paw out for handouts well into her 40s.  

Sorry, ended up talking all about me! Well done for telling your DH exactly how you feel.  He should know how close you are to jacking it all in. 

I can feel your pain from here. 

If you haven’t done a budget, that’s your first task. Make the budget then WORK the budget. Have weekly budget meetings with DH so he has to see exactly where every penny is going. 

I have to do this with my DH — and all our kids are grown and off the payroll. I resent the hell out of it but not doing it is the road to bankruptcy. 

So far it’s been easier for him to keep BM happy and you unhappy. You need to up your game so that he has an attitude adjustment. 

At 18,  It’s just bigger amounts of money needed.  As car, cai insurance, college, weddings.  Houses. And future GK.  Either you set up a budget right now.  Where DH gives you his fair share of living expenses each month. Or this is how life is going to be 

File for bankruptcy, put a freeze on all new credit, and separate your finances. If you don't want to divorce, then get out of the hole that has been dug and don't allow it to be dug again. Though, if he's that bad with money, I'd talk to an attorney about your options that protects your finances from his stupidity. It may be that you'll have to divorce on paper to prevent him from racking up more debt.

And maybe you file for legal separation during the bankruptcy. Show him just how fed up you are and that his actions while you both recoup your finances will determine if the separation leads to divorce or if it leads to reunification. The legal separation *should* protect you from his stupidity if he tries anything stupid and will give you breathing room to see what you can make of your own life, even if you stay living together.

Basically, talk to a bankruptcy attorney and lay out the plan that DH will follow unless he's cool with divorce. You'll be paying for his mess anyway, so he can choose whether you address it together or separately.

His response is always the same - he gets huffy and depressed about how hard he works without getting anywhere. When its bad enough he talks about wishing he was dead, then everyone would be better off because we'd have insurance money.

And does he realize why he is not getting anywhere? He is putting himself, and his family, in this financial situation. Shame on him.

There are so many good comments above, so I'll just add this...

I saw on your other posts you are working with some sort of budget.  Have you and DH agreed on what the priorities really are on that budget?  I mean it's great if our teenagers can all have cell phones, cars, and look forward to debt-free college, but in reality, those are privileges and luxuries, not necessities.  If you can't afford it, you can't afford it...period. 

Even if SD17 is basically a great kid as you've said before, that doesn't mean you have to go into debt and sacrifice your marital/family harmony to provide a perfectly capable teenager with luxuries that she CAN work for herself.  If she isn't working, why does she NEED a car and therefore car insurance?  Maybe give her a deadline to get a job and foot the bill until then.  If she doesn't do it then she can take the bus to school, have a friend pick her up, get that job she's avoiding, or BM can choose to suck it up and pay herself. 

As for the money drain continuing after she turns 18...only if DH has the extra to give.  Otherwise, there are personal/student/home/car loans, grants, scholarships, work-study, and a million other resources that SHE can tap into as an adult.  If she ends up sitting around on her entitled hiney after 18, well then she can hang her head and walk into the local public assistance office.  

It just sounds to me like DH needs to come to terms with the reality of his financial situation, prioritize, humble himself and have an honest chat with SD17 about being grateful for what she has and working hard for what she doesn't.  That's never easy to admit to your kids that you can't afford a certain lifestyle, but it sounds like he is risking losing all that is good in his life because he can't say a simple, "No, I'm sorry, but I can't afford to pay for that."  That is so sad if that is what brings you to divorce.  Again, I'm so sorry you are feeling so torn right now.  I hope he sees the light!

I'm so sorry.  :(  I can relate to the general sentiment. I will never understand why men think "taking care of their kids" only applies to their first family. Unfortunately, it's probably bc they think WE are on top of it and can take care of the shared little ones. My SO constantly is saying that he wants to put more effort into SD bc he doesn't trust BM to do it - WELL WHOSE FAULT IS THAT?!  ::facepalm::