Thats almost a carbon copy of my families story. My older brother and I got our new dad at ages 3 and 5. My brother joined the Navy out of highschool, and didn't like it and went missing for a while. He made a lot of wrong choices and caused a lot of problems for our family.
Now, he has a great job, lovely wife, and 3 of the most beautiful kids you've ever seen. It just took some time for him to grow up. If he'll stick it out in the Marines, he'll find a purpose.
Nature vs Nurture, Lodge... Nature always wins...