Once the conversation defers from the kids, END IT, politely yet firmly, "this does not pertain to the kids, and I do not feel like discussing the subject matter, goodbye".
I initiated this approach too late in my sitch. It did get my XW to think about things and be more rationale and maybe almost have a chance, but again, it was too late, atleast to save the M.
So if you don't want to heed that advice and continue to be a doormat, that is your decision alone to make and things will just get worse.
Me 35/XW 33 S13 & S12 M: 10/17/98 OM & S: 07/08 D final 06/09/09 12/03/09 - 06/13/10 "Piercing" 06/13/10: Engaged to Re-marry 10/17/10 06/25/10: Expecting baby #3 2/14/11