To suggest SIL seek legal advice (divorcing my brother)?

[SquarePeggyLeggy]

So my brother has decided that he’s not in love with my sister in law anymore and so is ending the marriage. They have 3 kids 9 and under.
He announced this 6 months ago, but has not started divorce proceedings and he won’t leave the house or even discuss doing so.
I think he’s being a total dick, his wife’s mental Health is terrible with this situation, the kids are sad.
What I’m asking is: can he do this? Just refuse to leave? Is it a grab for possession of the house? They have alternating weeks with the kids but it’s all in the same house. I feel like advising my sister in law to seek legal advice about this.

Further clarification, I don’t know either of them very well (much older half brother), but his wife is confiding in me a bit. She attempted suicide 6 months ago but called me first, I was surprised, and I now have her parents contact details etc. I’ve spoken to my brother a bit at the time, but we would see each other twice a year or so usually.

Seeking legal advice is sensible for your SIL. If he won't start divorce proceedings then she can. Either way she can make a claim for universal credit (if in England) if she is financially dependent on him. She can't force him to leave if they both own the house but she can divorce him and either they agree to sell the property or the court could order the sale if he refuses. It is important for her mental health to get out of this situation if it has driven her to a suicide attempt.

I guess I’m wondering if it’s my place to suggest this or whether I shouldn’t get involved. Thanks for the info, I didn’t think a person could just do this!