My mother in law always compares my son (whom she loves) to her other 3 grandkids (which she adores)?

its very annoying and shes rubbing it in my face bceause her one granddaughter is the same age (2) as my son and shes pretty much potty trained and my son just started telling me when hes done #2 of course hes already done it but its an improvement. im sick of it when has anyone else started training their son and how long did it take?? i figure im going to really concentrate on it a little bit before 3 that way he understands more, is this good or should i try more often now? and remember to answer how long it took your sons?? thank you!