My mum seems a bit obsessed with my son and its really getting to me?

my son was is 18 yrs old and i had him at 23.the first 2yrs of his life were spend at my mums house so i do understand why they are close.problem is my mum dotes on him so much i feel shes overtaking my role as his mother.she was very distant and never helped me or my siblings when we left.even though we all had kids ourselves.she seemed to resent it even when we visited her.my upbringing involved an alcoholic violent father who regularly beat her,most of which we were witness to.since my son left home she does nothing but fuss,give him money.where he stays he only has to pay �2 rent and ive just found out that he could be evicted because he hasnt paid.my sis and mum knew all about this and some trouble he,d had with police and didnt tell me because"i had enough on my plate already"i had a fallout with my son(usual teenage stuff)just before all of this.i feel as a consequence of my mother bailing him out of his money problems and basically treating him like hes her son that hes becoming lazier and has got no incentive to get a job.when i enquire i get the usual 'whatever' attitude from him.dont know how to approach my mother about this as anytime weve moaned about our upbringing she cuts us dead and says"well i was married and had 6kids things were different in those days?"as if that gave her a license to expose us to all the crap we saw?my son needs to be left to his own devices to wake him up and get him off his backside,unfortunetly my mother thinks he can do no wrong and if i ever moaned when or after hes lived with me,she cuts me dead and says ah well and changes the subject.maybe im wrong but im getting more and more resentful and feel pushed out.