My exwife filed divorce. but i didnt receive the summons. she had the judge give her default after prove up. can i still file my response to her”

I regret to hear that you received a family law default judgment.  Fortunately, most states afford revisory power to trial courts in the event of extrinsic fraud.  Extrinsic fraud is a type of fraud that prevented you from being heard (i.e., lies about you having been served, which permitted court proceedings to go on without your notice).  This is different from intrinsic fraud, or fraud that forms the basis for a cause of action.  Many lawyers have trouble with these concepts so, without getting too philosophical, suffice it to say that you are a victim of the correct type of fraud that permits a court to exercise its revisory powers - extrinsic fraud. For these reasons, the best advice would be to immediately retain an attorney to file a motion to vacate the judgment due to extrinsic fraud.  Evidence that you were not served will have to be attached to the motion (i.e., the affidavit of service filed by the ex-wife states you were served on date X at Y location, but you have a football game ticket showing that you were at a football game on that date at that time, and you also have an affidavit from your friends saying you were there as well). One final thought.  If you did file anything in the action challenging the proceedings (i.e., a motion to vacate the order of default), and if those requests were denied, then you may want to immediately consult with an appellate lawyer.  There are strict deadlines to file an appeal - typically 30 days in most states - so it is imperative to act quickly if you asked the court for relief while the case was ongoing but those requests were denied.  You might also have appellate rights, even if you made no such requests, if the court made a child custody determination without hearing from any witnesses or evidence.  This is because there is case law in most states providing that, even in an uncontested case, a court must still hear from someone or review something before making a decision regarding the best interest of a child.  So, if the court ruled purely in a default fashion (meaning no evidence at all, just a ruling), then you should also seek appellate counsel.  Otherwise, focus on the advice in the first two paragraphs of this post.