Ignorance discussion

so....does anyone have any idea the significance of Josef referring to Irena as "my sister" in the letter that he left at the hotel room?

The way I see it is that Josef viewed Irena as a "sister" in the sense that they have a type of solidarity with one another in that they were both emigres who had fled Czechoslovakia and then felt alienated upon their return to the country (now the Czech Republic) years later. Because of these similarities in experiences, Josef and Irena share a special bond with one another.

They are brother and sister in the sense that they both come from the broader "family" of Czech emigres.

He states somewhere that all his life he wanted a sister, but never had one. Irena made him 'feel' something warm inside, in spite of himself, and that is why he felt she was a kind of 'sister' to him. It isn't just about having lived similar experiences, it is about her and how she made him feel, I think.