How about making something from this ?
Dear XXXXX,
You must know how sorry I am that you and ????? have parted, and if you feel that I haven’t been as supportive of you as you would like, I can only apologise and promise to try to be a better friend, in future.
For some while now, as an outsider, it has been obvious that you and ????? have not been completely happy together and I felt that my presence would only make a bad situation worse. I felt torn to see my friends* arguing so much and, if I’m honest, I stayed away so that I wouldn’t cause any greater problems. It was a helluva long way to travel to find myself stuck in the middle of a marriage breakdown and I felt I’d be neither use nor ornament and both of you would feel bad on my part !
I understand how difficult it has been for you to settle into your new apartment and hoped that you would take me up on my offer to visit sooner, but thought it best to leave you to sort out the practicalities before imposing myself.
Now that you are sorted, when do you want me to come and see you ?
* remember they may reconcile !!!