Is not communicating with siblings except in emergencies considered a severing of kinship ties? And what is the correct behavior when shaking hands with the non-mahram sons of one's paternal uncles, especially if they consider the questioner like a niece and find it difficult to understand the issue of not shaking hands and covering the face, and is boycotting them because of this considered a severing of kinship ties?

Connecting with brothers and sisters is obligatory, and boycotting them is forbidden, whether they are full siblings or half-siblings from the father's or mother's side. As for the sons of the paternal uncle, they are not among the kin whose connection is obligatory. If you connect with your brothers and sisters in some circumstances, you are not severing ties of kinship, and the degrees of maintaining kinship vary. However, shaking hands with the sons of the paternal uncle and uncovering the face in front of them is not permissible. The ruling of Islamic law should be explained gently and wisely, and whoever relies on Allah, He will suffice him.