So I posted this in adult stepchildren but I felt this may be better since I wouldn't really call the problem coming from an adult.  Here goes. 
 

My girlfriend and I have been together for 4 years.  We moved in together about 7 months ago which was about 8 months earlier than we planned but due to her financial irresponsibility’s we had to move that time forward.  We were waiting for her oldest son to go to college. 

We both have 2 children. I have a 9 yo daughter a 6 yo son and she has a 12 yo daughter and an 18 yo son.  Yep you guessed it.  The 18 yo is the problem.  

Let’s call him John for this discussion.   Just a little background on him. Him and his sister have different dads.  My GF left his dad when he was about 2 years old. She had him at 21 and wasn’t ready for a child. They remained very good friends the entire time until about 3 years ago (will explain later).  She remarried when he was about 5 and again she left her last husband when her daughter was 4. 

Through the years John’s dad was an active part of his life and a great dad.  About 5 years ago his dad got a new girlfriend. John and his dads new girlfriend never got along. For good reason too. She is a little crazy. To the point to where my girlfriend and his dad no longer talk due to jealousy. Johns dad ended up getting his girlfriend pregnant and they got married.  He has been a deadbeat dad since then. No child support financially, emotionally, physically and is basically nonexistent.  

My girlfriend obviously feels bad for john so she lets him basically walk all over her. He is a good student. All A’s and honors classes. He got a scholarship to college and all in all is a good kid....the problem is he is lazy and takes no responsibility for anything.  

At times he is disrespectful to his mother, doesn’t contribute to anything around the house except when he is told(takes no initiative) and thinks the world revolves around him.  

When they first moved in we told him that we would buy him a car so he could see his friends since we moved 20 miles away from his old home and current high school(in south Florida that’s far lol). He has no interest in driving so his mom pays for Uber everywhere and for someone who’s finances aren’t in order is the last thing that should be happening.  On top of driving he also orders Uber eats all the time which also is a financial drain.  

I am very Money conscious.  Prior to them moving in I had a very balanced budget.  We agreed on sharing some of the bills which hasn’t gone so good either.  We often fight about her son and I feel like he needs to take more responsibility around the house. If he isn’t going to contribute to society like getting a job(I know right now isn’t the time due to the pandemic but it wouldn’t make a difference anyway) then he should be helping out around the house instead of logging 14 hours of PlayStation time.  

I come home from work and the garbage is full with another full bag sitting on the floor next to the garbage can.  The dishwasher is full of clean dishes and the sink is overflowing with dirty ones.  I feel like his mom enables him way too much because she feels bad about his dad.  Quite frankly I’m really getting sick of it. 

About 6 months ago when he turned 18 he took his money and opened a stock investing account.  To my surprise he did very well...to the point that we let him invest a small amount of our own money just for kicks.  We even told him we would give him a 10% commission on whatever he makes us.  Let’s just say in the first week he made us $2k. After that he told his mom he wants 20%!  She actually stood up for herself and said he should be doing it for free.  I gave him his commission and an advance because he mad a bad play on his account and a good one on ours.  He ended up loosing all of the money he made for us but it was a good learning lesson.  I received an email from my investing firm that another bank account was linked to my account and that a withdrawal was pending.  Basically John tried to take $200 from the account without me knowing.  That was after giving him $200 as an advance on future profits which never came.  I told my GF that he needed to pay me back the money but without a job it’s kind of hard.  

Recently we have been doing some major renovations to our landscaping around the house. I told her I wanted him to help. He has maybe put in 3 hours of work to our 80.  He sleeps all day and plays video games from 4pm to 6am. It frustrates me every day.  The fact that I have my career and a second home business and have a very strong work ethic. I feel like my GF and I shouldn’t have to do things like empty the dishwasher and take out the garbage after working all day.  

BTW We are both on the front lines of the pandemic.  

So with this frustration I try to talk to my GF about it and she turns around and gets frustrated with me.  It’s basically the only thing we fight about.  How do I get through to the both of them.  Should I confront John and possibly make things worse?  Should I continue to bring it up to my GF and destroy our relationship?  I keep telling myself that when he goes to college it will get better.  Another problem is, he is getting an apartment with 3 other friends for college instead of staying in the dorms(another bad idea I feel).  He has no life experience. Has never had a job. Doesn’t have a drivers license.  Can barely cook for himself and he wants to live in his own.   I am completely lost.