What you need to know to understand the following conversation is that our kids are bilingual but very much keep one language for each person. So Simon and I always speak English to each other, and the kids too always speak English to each other.
I had just corrected something Simon had said in English.
Me : It's like that in French but you can't say it that way in English.
Simon : I prefer French anyway.
Me : D'accord, si tu préfères le français, on peut se parler en français ! ("Ok, if you prefer French, we can speak to each other in French!")
Simon : Mummeeeeee!
Eve : Je t'aime, Simon!
("I love you, Simon!", deliberately said in French, which is not the language she usually uses with Simon, and which he had just protested about my using to speak to him. Cheeky girl!)