Step child's bio mom

So my 5 yr old step sons real mom finally showed her ugly face hasnt seen him in 4 yrs she found out we are expecting and now thinks she can come see him and get him and take him to who knows where the last time she seen him he was 1 she has no custody at all over him she lost her rights with her meth addiction and she outright doesnt see him her boyfriend is pushing her to go for custody she "now" cares about him cuz she heard about our new baby and i am adopting the 5yr old fully when we can actually get married he calls me mom or Brandi but most times mom she apparently is filling for custody from us but i am sure it wont get granted she had another baby but gave her up for adoption cuz it wasnt her boyfriends the 5yr old doesnt ask questions about his BIO mom so we dont talk about her or bring her up if he seen her in a store he wouldnt know who she was so why rip him away from the ONLY family he knows from a STABLE family and a STABLE life because your mad now about the new addition to our family

Sorry had to rant it out!