Important to keep our thread active so I will add a couple of items. Jesse and Lee were born but four days apart. I think this lent a degree of familiarity and comfort for Casey. She does seem to like her brother & there were qualities in Jesse that she found similar.
Casey and Lee have a powerfully different experience of their mother. Casey's Moon in Cancer afflicts Venus in Aries. She never faced discipline for rudeness or boorish manners. Bad manners were on display and of course, would be mimicked. Casey was sensitive (Sun & Mercury in Pisces) and her feelings were often hurt and offended.
Lee has a Capricorn Moon conjunct Mars. This Moon in detriment demonstrates coldness. Ambition was thrust upon Lee. He was treated or handled with impatience and insensitivity. Lee has a strong will and growing up, he was engaged in contests of the will within his family. He resisted domination but should not have been put to that challenge. He was up against a controller. His Venus is conjunct Uranus, which hardens his will but destabilises relationships due to the sudden disruptions of Uranus. As with many Scorpios, the opposite sex sibling was favored and he was strongly aware of it.