Being step mom can be 'tricky'.
I don't know whether it's normal or not, but he isn't your kid so you should not *waste* any energy in trying to parent him. His actual parent thinks it's fine (even if that parent is wrong) and you can't really fight against that (btw, I'm a stepmom to two young adults and *survived* their teen years by almost totally ignoring how they were being parented...doesn't mean that I ignored them, though, just the parenting).
My advice to you is to ignore the fact that he's sleeping. Make all the noise that you normally would. Just live life around him, paying no attention to whether he's awake or not. Leave the stressing up to his dad. If dad isn't stressed then why should you be, right. Stress is bad, don't take it on when it's not your problem.
I swear, my stress almost disappeared when I stopped worrying about how my step-kids were being raised. Despite their parents *incompetence* (LOL) the kids managed to grow up ok (and both moved out shortly after their 18th birthdays...yay) and become productive members of society.
I agree with
That sounds so much like my middle ds who is 16 1/2, and lives with his dad. My dd who is 13 just returned, and while she was there as well, she also had this same routine/pattern. The kids stayed up until 4 or 5 in the morning, and wouldn't get up until late afternoon. This is perfectly acceptable to their dad, but once school begins for my ds he will have to get back on track.
I agree with Rose, and this is true. Teenagers have difficulty going to bed early (earlier than 10pm) and waking up at 6 or 7am for school, their clock is different than that of an adult, they really aren't being lazy or difficult to rise in the morning.
I'm not a step parent, but I'm remarried and my dh has learned to pick and choose what is worth bothering him and what isn't.