Losing a sibling is difficult for anyone, but I imagine it's all the most devastating and difficult for twins. And the loss seems to especially painful for an adult identical twin who wrote into the Am I the A-Hole subreddit recently.
On top of losing his brother, who looked identical to him except for their facial hair, he is grappling with a nearly impossible dilemma due to the way his sister-in-law has been dealing with his visits to help out around the house.
It seems the sister-in-law has been using his resemblance to her late husband as a way to avoid broaching the difficult topic of death with her 4- and 2-year-old kids. The major problem on top of the grief he must be experiencing is that this widowed mom is letting the kids think he is their dad, not their uncle.
"I've been at the house often helping out with the kids and doing whatever I can with them," but as a result of him being around so much, he also feels like his brother's widow is using their resemblance to avoid the difficult conversation with her kids about daddy being gone for good.
While he's very clear that she hasn't made any romantic advances toward him the problem is "I also believe in her mind this is how she's coping, by pretending he isn't really gone because she 'technically' does still see 'his' face everyday."
He's gotten to a point where he doesn't want to be complicit in the charade anymore, but he's struggling with whether to wait until she's ready to tell the kids about their dad or take the matter into his own hands to avoid letting the situation "snowball ins't something far worse on the children AND her."
It sounds like the implausible premise of a movie on its face, but reading his response to the commenters in the AITA community, he seems pretty genuine. A lot of people immediately suggested grief counseling — both for OP and his sister-in-law.
In the comments, he shared that he is getting the help he needs but doesn't believe his SIL is in therapy currently. He also clarified that he isn't actively participating in some sort of charade. "I don’t let her continue the charade, I unknowingly stepped into it when I began going over to help and babysit and they began to think I was their father and she didn’t put a stop. I’m trying to find a stop to it, but there’s really no wiggle room here," he explained.
As is always the case with the more dramatic posts on AITA, there were a fair number of users who called BS on this man's story. "I wish it were a s--tpost and I could live my life without guilt but unfortunately here we are," he commented to one naysayer.
However, plenty took him as his word and offered really helpful advice. Annabel1231 compassionately pointed out that, whether his sister-in-law realizes is, OP's being prevented from focusing on his own grief. "I think you all need to go to counseling because this is well beyond the capabilities of reddit or dealing with yourself."
OP said it has come up in therapy that he tends to not get hit by tragedy immediately and "my therapist had mentioned that maybe it’s why my SIL seemed to put me in this position, because I’d held up so well." Annabel also suggested some language OP could use to establish he is "Uncle J," not "daddy," which he said he would pass onto his SIL.
In the mean time, it also sounds like he may try to spend less time there if he doesn't see his sister-in-law is addressing the reality of the situation with her kids. Here's hoping this family can find a way forward together through their loss.