first off, good for you for leaving your ex boyfriend.
no one deserves to be in a relationship like that, if the person treats you like they would a carpet, they are not worth your time of day. be with friends now to help you cope with this.

second, i know this is not how you would have liked to find out about your brothers having a relationship with your dad, but maybe you could mention it to them, saying you accidentaly saw the messages while looking for the alarm.
it sounds as if they are standing by you, because they knew that if you heard they were talking to their father now, you might have gotten upset..maybe they were protecting you from this and were waiting for the right time to tell you.
if they want a relationship with their father, it does not mean that you have to accept him back into their lives, but maybe they just want some sort of relationship with their father. and it does not mean that you are beaten by this whole thing again, and it does not mean that your family does not care about you and thats why they have not told you.
mention this to your mom first, and see what she says.
i feel that maybe they hid this to protect you.
do not speak to your ex. he sounds like a worthless piece of ____.
you do not need an abusive person in your life, you deserve so much better, and can do way better. no one should have the authority over what you do or control you abusively.
like i said, take this time to see your friends, hang out with them and do things together, talk to your best girl friend about what is going on and maybe they could help you with this. you can find someone way better that than guy.
you can fight this, i bet you are a very strong person to have gotten through something like this before, and im sure your mother would be glad to hear what you have to say about all this too.
things in life are always looking for ways to bring us down, if we stop fighting to gain happiness in our life then whatever it was that took away that happiness has won. and you are much stronger than that.
keep fighting, things only get worse before they get better. and things will get better.

good luck hun, if you need to talk you can always PM me anytime.

stay away from your abusive boyfriend. ive been away from mines for two years and i still suffer from what he has done, or said to me.
your family loves you but they probably didnt know how you would react to the news. dont put so much stress on your heart, sometimes you have to not care and let go and let God. meaning somethings we cant control. your probably trying to handle all your problems when the bible tells you to but your burdens on christ.
as long as you dont have to see or hear your bothers dad, you should be fine. i would express my opinions in the matter if i was you. i m sorry you have to go through this.
and another piece of advice, please be careful with the next guy you talk to, dont rush into a relationship, get to know the guy...you might not like him.