Relationship turned to „friendship“: what would you do? Advise appreciated

Relationship turned to „friendship“: what would you do? Advise appreciated

Obligatory English isn’t my native language. I am also typing on the phone, please excuse formatting and grammar.

So, this story isn’t about me (30f) but my SIL (32f). She is in a 9 year relationship with her bf (let’s call him BIL, 31m), they have a son (2m) together. Last week, MIL called my husband to tell us that BIL broke up with SIL because he „doesn’t love her anymore“ and that he has felt like that for a while. SIL later explained in more detail what happened: he sat her down and said that, for quite a while, he feels that they are more like friends/roommates than a couple and would like to go separate ways. However, rightfully so SIL asked him why he never said anything to her. Then could have faced their problems and at least try to work on it before breaking up. Well, he isn’t really the type of guy to communicate his feelings but rather bottle them up… and well, that’s the outcome. However, during their talk BIL seemingly was open to at least try and work out whether they can save the relationship. SIL still asked to him sleep at his mothers place for a while and that’s where they stand right now. They are spending some quality time together without their son to talk etc.

Now, MIL was pretty angry at BIL at him, but more because he actually feels like this, not because he is being unfair or mean or something. She was like „They have a child together, of course their relationship is gonna change, what does he expect? He can’t just back out of it because of that“. While I get where she is coming from (she is mainly having their son‘s well-being in mind), to brand him as selfish or something didn’t sit well with me. BIL has the right to feel how he feels and he is not obligated to stay in a relationship he is not happy with and surely SIL doesn’t want to be with someone who doesn’t love her either. „Think of your son“ isn’t imo a valid reason, because he can be a good father (which he is) even if he chooses to leave his gf. Parents that are together don’t equal „good“ parents and unhappy parents are surely as bad for a child down the line. And I certainly would feel really shitty if my husband didn’t love me but stays with me just because he thinks he has to or is pressured to do so.

Anyway, while BIL has the right to feel how he feels, he certainly should have communicated his feelings waaay before it got to this point. Now SIL feels blindsided and is justifiably upset, because apparently he never mentioned that he thinks their relationship is deteriorating. After all, she can’t change if she doesn’t know that there is a problem in the first place. I am not saying that she didn’t do anything wrong because she knows herself she is responsible as well – but communication is the key, right? Obviously, the trust in BIL is gone because now she knows that he „doesn’t love her“ as a partner anymore and it’s very hard to ignore that.

Imo, counseling/couples therapy is the way to
go. In no way is BIL able to „sort things out“ on his own, because that’s what he’s been doing the entire time, didn’t he. If he truly wishes to try and save the relationship, they both need outside help to work on their communication and explore their feelings. I think SIL said so as well but BIL doesn’t seem open about that, at least right now.

And that brings me to my question: how could a couple recuperate from such a situation, when one partner „fell out of love“? Let’s leave the son out of the picture for now: What should the „leaving“ partner do at best, what the partner who is left? How can the trust be regained? Open communication, quality time together, therapy, breakup and stay amicable if all fails… what else are valid options and methods? What advise would you give and what can others learn so their relationship doesn’t suffer the same, very common fate?

I would love to hear your opinion and experience! And no, this is truly not „actually about me“ lol

TL;DR: SIL and BIL are about to break up because he „doesn’t love her anymore“ as partner but rather as a friend, but is open to at least try and save the relationship. What would you advise for this to succeed?