I do agree. Either both kids have a key or neither does, and I have said I think he needs a key.
I think there is a lot of exaggeration where ex wives are concerned, just the same amount of exaggeration about how shit some peoples ex husbands are. There is one side of a story, the other, and then the truth.
I think you do have to consider, though, that some people really are unhinged, these people do exist. Whether op is telling the truth or exaggerating I don't know, but you have to accept that some people do get stalked and it is serious.
Like I say, my dp never said a bad word about his ex and until she found out about me (3 years and 1 relationship after they split up) they were amicable, everyone was happy. Then like I say she punched my dp in the face in front of their son, dps parents and me - because he had the cheek to introduce me to his own parents. Some people really are unhinged. Before that incident I thought his ex was a nice, normal woman and I would have quite happily had a civil relationship with her. Since then, she's threatened to kill me, my dp. She would not let him see his son at a moments notice, she would speak to his parents, find out what we were doing and then change the days he had his son so we could not do what we had planned. I could go on for days what she's done, and none of it is what dp has told me its all things she's said or done to me first hand.
Not everyone's ex wife is like that, but some are.