First up I've name changed so as not to out myself or my brother, who I'm trying to get advice for please.
DB has been married for 13 years, last year his wife asked to separate. She denied it but he suspects she'd had an EA with another man and that was the point at which she decided she'd be better off without DB, although he asked to reconcile. They have young dc and wanted to keep things amicable and go down the 2 year route.
Since then DB has got a new gf, they seem pretty serious. STBXW may have met someone else too but hasn't gone public iyswim, unlike DB who is making no secret that he's met someone special. STBXW is now making noises about speeding up the divorce which would mean one of them being "at fault" in some way. DB doesn't want to put something like that on record and to start writing down accusations. STBXW would want to be the petitioner as she doesn't think the marriage breakdown is her fault. Can she just go ahead and file for divorce if she wants? Could she cite adultery as a reason given DB's new gf? Would it matter if she did, really, in the scheme of things - I completely understand that DB would be gutted to be "publically" put down as the one at fault, especially as he doesn't want the dc to think badly of him in the future. But is it in fact a pragmatic thing to do, to just get on with things?
DB has grounds to file too - she's run up a massive debt which he's now having to repay, plus she is the one who walked away, wouldn't reconcile etc. But I don't want to encourage him to get into that as I suspect it might get nasty. Does going the quicker route usually mean things go sour? I can see that it might benefit DB to make this break sooner but not if it's going to end in acrimony, especially for the dc.