I suspect I am a being a bit sensitive towards the MIL, who is generally ok, but it drives me crazy that when ds and I visit, we will have been there all of 2 minutes, sometimes less before she points out something that ds is doing and says oh yes A (their other grandchild, ds's older cousin) always used to do that, or oh A was so funny the other day, she did xyz and off we go on a long story about what the grandchild who is not there did.
I know she sees far more of A than she does of ds but that only makes it worse - feel that she should focus on ds and not constantly be referring to granddaughter all the time.
In some ways it is funny, I have bets with myself as to how soon she will mention granddaughter within our arrival, once it was less than a minute! But it does annoy me too.
Rant over, feel better for that.