His parents are... not here. Maybe they were shot in an alleyway and Jack became an orphan instead of being taken in by Alfed? Or maybe this is part of his Walking the Earth routine where he will learn the stealth, martial arts, and synchronized dance techniques that will allow him to clean up the mean streets of 1920's Gotham?
Oscar states in the musical that his father didn't take care of him. In addition, they live with Wiesel, who, in the film, one of the boys refers to as their Uncle. Oscar and Morris show a tendency toward unnecessary aggression, and are violent beyond what their job requires. Morris in particular shows a desire to use intimidation whenever possible. All of this is commonly observed in abuse survivors who never had the underlying issue addressed. It would also explain the amount of anger that can be seen in these characters despite the fact that they are children, as violence is often a learned behavior.
Most, if not all, of the newsies in that lodging house are either gay or bisexual. They sleep on top of each other and are very close. One of them even humps another guys leg in bed at the beginning. They just have sex at night because they don't want others to know. Remember in the 1890s, homosexuality was illegal.