It's interesting to follow the development of language between BK1 and BK2.
When they are playing they often switch to English, especially if they're pretending to be someone else or something else. They have done this for a long time, even before BK2 started attending pre school.
But when they discuss something serious or switch to talking about what they play, they switch language immediately.
Amazingly, they have different preferences: BK1 always switches to Arabic while BK2 uses German as much as Arabic!
I have no explanation for this. Is German easier for BK2? Maybe.
The funny thing is that whoever switches away from English first sets the language they both will use, at least for a couple of phrases. They will then invariably fall back to Arabic at some point before they go back into play and use English again.
Funny, isn't it?