Is it Islamically forbidden for a sister to kiss her brothers, and is a fiancé entitled to prevent her from doing so?

We previously explained that a brother kissing his sister is permissible in principle, with certain restrictions. However, some in our time may forbid it as a precautionary measure (sadd al-dhari'ah) due to the spread of incest. If this is the case for kissing, then it is even more so for the described fondling, which are ugly actions that you should not allow your brothers to engage in, for fear of undesirable consequences. We also draw attention to the fact that a suitor is a stranger to his fiancée before the marriage contract, so it is not permissible for him to speak to her except out of necessity, while observing the Sharia guidelines.