What is best way to handle 12 yr old ex step son's influence on my 6 yr old boy?

[DaddyDad2]

Recently, my son's mother decided she wanted visitation.  She has a son [12] from another marriage who used to be my stepson.  I shared the excitement with my son that his mom and half-brother were now going to be in his life.  I kinda had to since she basically only had to ask the judge and got it.   She could have asked me but that's another post entirely.   

The point is, however, that since the see visits began, I started to notice behaviors that I'd forgotten about that were all too familiar.  While not necessarily a bad kid, my former stepson has some rather annoying sounds and faces he makes out of no where that time had blurred in my memory.  He also blurted out random words or phrases like "your momma!" Now my son is doing these things and it's beginning to wear on me. 

As I did with the stepson a couple years ago, I asked him to stop and he does, but it comes right back.  His mom used to get annoyed with her son for it but if i made mention, she'd say I hated him.  I disliked the behavior, not the kid.  I don't want to make my son distance himself from me by hounding him about it, nor do I want his mom to indicate I am not "fostering" their relationship (as I was "ordered" to do).  So what, other than suffer in silence (my own), can I do or say that will temper this behavior?

For the record, i have been around  kids plenty.  This is beyond the norm, and my son was not acting like this before.  It's a bummer but I'm feeling as though anything  I say or do further to correct it will only makes things worse if anything.  That's why I'm here.  Any  ideas on how to guide my boy to not behave like his half-brother while avoiding being the "bad guy?"

[Worriedparent1021]

When I was a kid I would go to NY in the summer to spend a few weeks withat my cousin. I looked up to her, she was very pretty and popular while I didn't have the best self esteem.
After spending a week or two with her I picked her her sayings and, believe it or not, the ny accent. It wasn't a conscious thing I was doing, I just was so used to hearing it is picked it up.
It would fade away, mostly because my sister would kind of make fun of me and embarrassed me about it. I was older then your son, I was 11. If I had to guess, I would say your son is probably so happy to be a part of his brothers life. They share a mom, correct?
He's only 6 and I'm sure he's thinking things like "why does he get to live with mom, but I dont" even tho I'm sure he's very happy with you.
So he probably idolizes the 12yr old and wants to be like him. Maybe just remind him that when he does these things,not only can it be a little annoying to others but it also isn't who he is. Maybe tell him how awesome of a kid he is and how you and his mom love him and he's perfect the way he is, and shouldn't "copy" things his brother does.
He might not even realize he's doing it.
Not sure if that helps at all, but maybe when you talk to him you can say something like "every time you act like your brother I'm going to say the word (pick and fun word) to remind you that your doing things he does"
I have amy 11yr old daughter from a previous relationship, and a (almost) 6yr old son with my current husband. My daughter hasn't seen her father since she was 4. She is angry and has a bad attitude. When my son acts like her I say to him "this is hoe your sister acts, it isn't ok when she does it and it isn't ok when you do it" sometimes he says ok, sometimes he gets more upset. They look up to their siblings, and they think their siblings are "cool" and can do no wrong.
Whatever you decide to do, tell your ex and ask her to please go along with it to break the habit. Not sure how she is but it'll be confusing to be allowed to do things with one parent that you can't do with another.

[DaddyDad2]

Unfortunately his mom is an extremely covert manipulator that one is better off NEVER discussing any potentially sensitive topics with.  I'm just going to gulp and provided gentle cues so he's not affected adversely.  He cannot help it. Theres always going to be something when he comes home after visits there.  If this is as bad as it gets, I'll be thankful and suprised.