I'm going through a divorce and my ex wife is calling my adult kids to testify against me. Can I object to this

Your ex-wife has a right to call any witness she desires if the witness is competent to testify.  A competent witness is an individual with first-hand knowledge of the facts in the case and possess the ability to testify truthfully.  However, the issue is whether the witness is able to offer information that is relevant to the issues before the court. For example, if this is a custody case and the witness offers information that has nothing to do with a custody case, you may wish to object to the testimony of that witness.  Once the question is asked, you could object on the grounds of relevancy.  The court has to rule on the objection before the witness is allowed to respond. If you do not plan to engage counsel, perhaps, you should consult with an experienced family lawyer in your area to help you prepare for trial.   Most lawyers charge by the hour.  Therefore, you should discuss the cost of a consultation before scheduling an appointment, to avoid any misunderstandings regarding fees.  Best of luck~