We told S5 together last Fall that we were going to be living separately, that we would always love him, and that each of us (W and I) needed time apart to get better. Since then, W has told S5 that she intends to stay apart. I haven't joined her on this - quite frankly b/c I still see it as we first described it. MIL/FIL tried to press the issue early with "never/evers" until I threatened W with court action if she didn't start to defend our son from their BS. So far, she's been keeping adequate boundaries for S5. S5 still has hope regarding reconciliation, and he clearly knows that I'm the person to listen to his hopes - not W or her family.
I've read that in adolesence, its harder on girls. But each child is different.
