> I still feel and share a bond with him that I'll never have with my other siblings and I can't quite explain it.

May I bother you with a request for perspective? A neighbour lost one of his identical twins at 6 months old. Both twins were born around 700 grams, and were under treatment (incubation possibly, but I'm not sure) in the house for many months. I do not know if they were together during treatment or not.

The twin who lived does not know that she had a twin sister - at around age two or maybe three the family took down the photographs of the deceased twin and stopped talking about her. Might that have some lingering effects on the living twin? Of course I'm asking about the general case, not this specific case, because obviously I cannot provide enough information over a short HN comment. But in your opinion, as someone with an unexplainable bond unlike that with other siblings, might such a bond persist even had you not known about the existence of your twin? How might that affect you if so?

To be clear, I have no intentions of revealing what I know and would never betray the parent's wishes.