I get exactly the same! It really used to upset me but if he is saying it to you then he is most likely saying he want to go to mommy’s every time he doesn’t get his way at his dads…!
In your case do you think it is because dad let’s him stay up late, eat not so healthy stuff…? Do you discipline more ?
I only ask because it’s the reason my little boy says it – although I do think these little ones are very clever, they definitely know how to make you feel inwardly upset