If it is "not alimony", then the entire pension is taxable to you and you can't make any adjustments for what you pay your ex.
However, you can ask the family court for a QDRO, qualified domestic relations order. This is an order from the court directing the pension payer to pay part of the pension to your ex. Your ex would get a 1099-R for the part paid to them and your 1099-R would only show the part paid to you (starting from the date the pension payer processed the QDRO, of course.)
