Thanks for your response.

Regarding the Suffering Servant material, the Church obviously has an interest in making suggestions that support its agenda. It is by no means certain that if refers to or prophecies Jesus. See for example this recent article by the very knowledgeable Evan LeBlanc:

https://medium.com/backyard-theology/isaiah-53-part-i-daf9340447af

The issue of Issa (Jesus) in the Quran is very difficult to get to the bottom of. Because both names can be rendered as Jesus, even some Muslims can be confused. Some of the material we can reasonably assume refers to 'our' Jesus, although it is controversial, namely that he was not crucified, also that he was not the Son of God, rather a prophet. Some of the other material is more doubtful, as discussed in the article. I did at the end provide a link to an earlier article which goes into much more detail. If you have time you could read that and see what you think.

With regard to the sister question, I obviously accept that it might mean fellow member of a particular group, especially in modern times. I'm not sure that is what it means in context in John's gospel.