The opening sentence is unclear. You have written it so that the parents fate and the brother's fate are separate, but it is not clear whether you intended that. Also, it is not clear why the sister gets placed in a home, but the brother gets deported. There might very well be a logistical reason, but there are too many questions.
"...whose ugly secrets are hidden within the walls of their home." This makes me think that there is a body hidden in the walls. But, since you say "secrets," I think there may be more than one. These guys are foster parents?
So, the blurb implies that the girl finds out about whatever the secrets are and is frightened because of them, not because of the situation her family is in. So, it is unclear why the girl is in flight. Either of those reasons would be compelling.
I wouldn't use the word "rash." She may be desperate, but whatever decision or action she takes is probably not rash. Unless you want to say that she is in a blind panic. Many children are, not saying that's wrong. Just that it is unclear what's really going on.
"Her dangerous saga redefines her understanding family and home as she must grow up very quickly in order to survive." This just can't be the hook. This doesn't work at all. It sounds like an afterthought, something you say just to get off the page quickly.
It also sounds clinical. This is one reason why authors resort to asking questions at the end of a blurb. Those let the reader decide a proposition and whether they want to find the answer by reading the book. I don't advocate questions. But, they are one step up from your ending, no offense intended.
Your blurb is too short unless it's going on the back of a movie jacket. Enlarge upon this "coming of age" idea and lengthen your blurb a bit, and twist it so that there is a good hook. For instance, you might think about what is going to happen to that awful foster family. Because I don't know your plot, I can only guess about what they did, and that it's something quite evil, and they deserve punishment.
I doubt very much that a minor child can affect the outcome of any deportation or criminal proceeding--and, maybe you have a solution for that!--so, I think that perhaps concentrating on how she gets away from pure evil might be a hook of sorts.
One more thing: do you really want to imply that there is a feel good solution for this awful, very current, situation with this child? What age group are you aiming for, and what is your intent? How you state this situation depends on what you are going for. As I reread your blurb, it seems to me that the child could simply end up on the streets. That's a dark ending. Could be true, and it is heaped in facts about what really does happen to foster youth. What's your intent? For your particular blurb, the last paragraph is more important than any other.
Good luck!