My ex husband (I have been divorced 14 years) recently informed me that if anything happened to me and our son then the house we live in would become his. My will leaves the house to our son. My ex didn’t contribute anything to the house, so I assumed it would go to my family.
Assuming a final order was drawn up at the conclusion of your divorce (you may want to check this) then neither of you will have any further claim on each other, subject to the terms of that order. I presume that your ex husband is suggesting that if you were to die, and then your son, having inherited the house from you, were also to die, then your ex husband in turn might inherit the house as your son’s next of kin.