WIBTA if i tell my best friend his girlfriend is planning to break up with him?

names changed for privacy

i (22nb) am really close with steve (27m) and his girlfriend sarah (24f). they have been together for almost a year and they were probably the most solid relationship i have ever seen between two people. unfortunately over the past couple of weeks, sarah has been confiding in me about some issues that she has been having with him. steve has been having hygeine issues, jealousy issues and been wuite manipulative frankly from what i hear from her.

conversely, steve has also confided in me about sarah and how he is beginning to feel unloved and not cared for because she has asked for a little space. he is EXTREMELY insecure but he is also my best friend, so i am always there to listen to him. he is so distraught and loves her so much and i know deep down he would change whatever she needed to be changed to keep her happy.

sarah came to me and said she is planning on breaking up with him this week because she can't forsee a future where she feels properly loved and cared for by him, along with some other personal issues in which she feels being single will be the best option for her. i completely support this and personally think it is the best idea for them both.

i know for a fact steve will be so unbelievably distraught and upset, and because he is my best friend i want to figure out a way to soften the blow before it comes. i told him i am here for him all the time no matter how he feels and that he can always come to me for support, but i am genuinely worried about his mental health if sarah goes forward with breaking up with him.

wibta if i pre-warn him?