Boyfriend and I are breaking up, what to do about kids?

As the title says, my boyfriend and I are breaking up. However, he has a son named Mason, who is the same age as my daughter (both are 6) . She is constantly talking about Mason, how much she loves him, when can she see him next, etc. For the most part, they act like they are siblings. She will be devasted when she finds out.There is no way she will be seeing Mason again. His father cheated on me and I want nothing to do with him. This breaks my heart because after the past 4 years, I've come to see him as my own son. We have acted like a family for so long, I don't know how to untangle her from this.How do I break the news to my daughter? Should I straight up tell her that she will never see him again? Would it be better to keep telling her "maybe next weekend we can see him" like I have been and hoping that she forgets? Should I just swallow my anger toward his father and still arrange playdates and hope their relationship slowly fades away? It's so unfair to the two of them that they have to lose their best friends due to their parents' behavior. via /r/Parenting http://ift.tt/2ueesbP