Love hate relationship

The title describes the relationship between ting and fu.

Whenever they're together, they will get into bickerings and fights. Ting will oppose to whatever her brother says (whether or not she understands them) then they'll start a shouting match of
"YES!"
"NO!"
"YESSSS!"
"NNOOOO!"

Or Fu will find whatever ting is holding more interesting than whatever he's holding and snatch that away from ting's hands. Then it will be followed by screams, squeals, hair-pulling, face-punching, etc etc..

Then today, when I told fu that I'll be bringing him (only him) to see Dr Bel, fu came into the room and pleaded with me, "mum, can u bring ting too? I promise I will not fight with her."

I had only wanted to bring fu cos his symptoms are more serious and it's really not necessary to bring both since I'm very sure both caught the same bug (incidently and embarrassingly from their mother). Nonetheless, I asked fu, "Why do you want mummy to bring ting?"
"Cos she's still sick!" was his immediate and as-a-matter-of-fact reply.

I didnt have to heart to reject him and of course ting was delighted to come along..