In the complex world of Family Law there must be precision in understanding the convoluted relationships of broken families and the new living arrangements. Standing is of great importance. Take the Brady Bunch, Mike Brady was father to the boys and stepfather to the girls. Carol Brady was mother to the girls and stepmother to the boys. Alice was just the maid. Got it? Mike and Carol were husband and wife; married.
So if you are the girlfriend, friend with benefits, fuck buddy, lady in waiting or fiancée to a divorced man with a couple of kids from his second failed marriage; you are step nothing. It would be an error of law to publicly represent yourself as the stepmother of two little girls based on your casual relationship with the father. Step status requires the legally recognized committment of marriage.
False claims to the public of being a stepmother is likely the manifestation of some underlying mental defect, incapable of understanding that familial bonds are required to achieve such exalted status. Otherwise you are just a delusional clingon screwing with the heads of kids to whom you are not related by blood nor marriage….like a crazy woman.