My MIL treats my SIL's son like a GEM. Everything is about him. My other SIL also feel that her own mum is biased. Every time we have family gathering, with all the grandchildren around, the boy gets special attention. Even though she say she is shifting in with us (we have a room well furnished for her), but she only sleepover for 1-2nights/week. Most of the time she sleep at my SIL place with the GEM. I feel that the room for her in my house is 'under-utilised'. I could have converted it into a playroom for my kids. And sometimes when she comes over, she brought the GEM to sleepover too. I don't feel good, kinda feel privacy intruded. Am I normal to feel this way?

It is certainly normal that you feel that way, your feelings are yours and yours only and no one can dispute it be it right or wrong. Moving forward. How would you handle this if this was your mother? =X All in All, they are old and not many good years left, let live and let live. I don't understand why would the GEM be an intrusion of your privacy, in fact is good that your kids forge bond with children within the extended family. Won't it be good that she only stay 1 or 2 days? Imagine if you said that, she might just choose to stay for more days and your relationship might sour because of that. Remember this is the mother that raise your husband. Traditionally daughter-in-law has to service the MIL, but thank god we are have moved pass that era. Still some of issue still exist, lets count our blessing. Lastly have you even consider why she dote the GEM so much? Could it be that the GEM is suffering from illness and was not disclosed? I recall a story my friend told me previously that her grandma always dote a cousin of his and it turn out that this cousin has terminal illness and die years later. I say this not to scare you and make you go probe and worry that the illness might spread to your child. but hope you can take a paradigm shift.