About Grandmother in Boy in Striped Pajamas

1) She had met Grandfather as a young woman after one of her concerts and somehow he had persuaded her to marry him despite all his flaws.(Grandmother loves Grandfather)
This shows that grandfather must had really strong emotions for grandmother when they were young. I think that since their relationship had fostered from a strong root, Their relationship must be even stronger now. Thus, we can conclude that grandfather still loves and respects grandmother very much.

2) Grandmother liked to think that Bruno or Gretel would follow her onto the stage and every Christmas and at every birthday party, she would devise a small play for the three of them to perform for Mother, Father and Grandfather.(Grandfather loves Grandmother and watches her shows)
This shows that grandfather still thinks highly of grandmother as he still bothers to respectfully watch her performances. This goes to show that they have a good relationship with each other and Grandfather still genuinely watches grandmother’s performances.
8) However, Mother and Father’s voices were muffled and hard to make out, Grandfather’s was not to be heard at all, while Grandmother’s was surprisingly slurred. (Grandfather allows Grandmother to air her opinions, love?)
This shows that grandfather respects grandmother’s views as he “was not to be heard at all” which shows that he did not interrupt grandmother’s loud complaints and just stayed silent. I think that grandfather may even be slightly scared of grandmother as he made very little attempt to stop her from complaining although he disliked it.