Husbands Family wants his Ex around

Irene
My husband and I have been together 7 years married 2. I'm 4months pregnant with our first and we have custody of his 11 yr old son because his mother is a drug addict. We got invited to a cookout at my husbands brothers house and were all ready to walk out the door and then my husband gets a call that his ex the mother of his son is there! I just don't get it... It's so annoying because I know my husband wants to be with his family but I am not going to hang out with a woman who chooses drugs over her own son. This has happened several times in the past and when we don't go to the family gatherings his family wants to know why??? Really!!?? 😟😠😤 I'm really sick of her always around I mean why can't she move on and get her own family? I don't know if I'm being over dramatic or not and it definitely doesn't help that I'm a big bag of emotions but I just needed to vent. Feel free to comment your opinions weather you think I'm cray cray or if I have a legitimate argument.