Well you're a very energetic little one, arent you? I don't know what the ending of your question was about but here's my answers and advice,
Yes it's possible to move in with an older sibling as long as they are over the age of 18, works and can support the family, and has permission by law.
Are you saying Aaron is going to have a relationship with his step-brother? Like a gay relationship? I suppose it's possible but kind of gross and close to incest. If Aaron is only 17 though, they can get in trouble by law for having sexual intercourse because Aaron would have to be 18 or older. It's considered rape by law.
Why would rape matter? If he loves her, he shouldn't blame her for what another guy forced upon her. It's not like she asked for it, correct? He can help her face her past with Ron.
Hello Departure is interesting. Maybe try another word before Departure such as Happy Departure or Total Departure. Im not sure on that one. Go with what you want, it's your story. But choose it because you like it, not because your friend told you it's "cool"
If you're having trouble with writers block, try some excercises. It sounds crazy, but the only way to get over writers block is to force yourself to write. A LOT. Try making up crazy short stories, writing a journal about your day, record your thoughts and dreams, or write a letter encouraging yourself to write, like a pep talk.
Stay motivated by making yourself a writing area. Mayby a desk covered with paper, pencils, erasers, pens, dictionaries and get some creative artwork/pictures to hang up on the wall. Add in some inspirational quotes. Everytime you think about doing something else, make a deal to yourself to write at least 4 sentences before you leave. If you're really discouraged, picture what it would look like finished. Imagine the pride you'll feel if you get it published. Picture it being a big hit show or movie. Look at other successful writers and their journeys. (Im currently trying to encourage myself to keep writing, so know you're never alone with writers block)
I don't know much about Fictionpress.com but if it sounds like a good site, try it. Also check out these books and websites:
Write Your Way Towards Home
They help with advice, tips and writing excercises.
It sounds good :3