Parental alienation is a custody term, not a separate cause of action. Since you already have a custody suit going you just present your evidence of their behavior at the trial.
The information contained in this answer is not intended to be legal advice as the drafter of the answer does not know particular details about your case. For more information please visit our website www.bakerbillick.com
Sign up to receive a 5-part series of useful information and advice about child custody law.