In Islam they have a very good basic rule for these kinds of things. If a man wants to have two families (as your father seems to have) he has to ensure to treat them equal. So if your father was treating his children differently - then at least this was wrong from his side.

These things are difficult - and I understand you snapped! Full reason for that.

Although I do not respect your father much - then I will still say - that he is trying his best - but his life as it has been so far - is of cause not existing - and in all likelihood his other family will have serious difficulties forgiving him for his deceptions and are probably very angry at him..

It will become better - will take time.