cloudme
well, i think maybe their thinking is that no need to split until so clear since the 2 kids are there and they're related, not in a nanny's place or childcare centre. I know one thing for sure, the elders won't bother with such hygiene or splitting of stuff coz they grew up with everyone sharing everyone's things.
If you're not comfortable with such an arrangement, then u need to talk to your SIL & MIL on your views abt hygiene. At least clear the air and tell them your concerns. Not that you don't wanna share, but coz of hygiene, just like having a meal on a table and the need for 'gong kuai' so that germs don't get passed ard. If not they will think you're just being selfish and don't wanna share.
My ILs were rather resistent to 'gong kuai' previously. I had to tell them many times, esp when one of them are sick abt the need for 'gong kuai' coz my boy is very weak and easily fall sick. Now they will auto put the 'gong kuai' there and separate bowls for soup.