Is the failure to ask about the father's children from his other wife and about the stepmother herself, and cutting off communication with them, considered a severing of kinship ties?

The kinship whose ties must be maintained (Rahim) refers to relatives between whom there is a prohibitory degree of relationship (mahramiyyah) and marriage is unlawful, such as ascendants, descendants, and those connected to them. Accordingly, paternal half-siblings' ties must be maintained through visits, inquiries, or gifts. As for the father's wife, she is not considered part of the kinship whose ties must be maintained merely by virtue of marriage, unless she is a blood relative. However, her ties may need to be maintained as an act of filial piety towards the father.