DS1(7) last year "I don't want to live with you anymore, I'll go with my real dad"
Bit of background. DS "dad" makes contact every few months and sees him for a few hours, sometimes a whole day. My DH is DS dad in every way and DS calls him dad too. When he sees his bio dad he always throws a strop and refuses to go, when there he's desperate to come home.
That day we had a bit of a meltdown over chores/bedtime/life and he threw that comment at me. I was so upset although knew he never actually meant it. He tried to apologise as soon as he realised what he said but it's stung ever since. I did give him a hug and told him I loved him though.