Is it permissible to give zakat to parents and siblings, and what is the ruling on forgetting the time of its निकालना (Hawl)?

It is not permissible to give zakat to parents on the basis of their poverty or destitution. As for someone who has not confirmed the completion of a full year (hawl) on the nisab (threshold amount), zakat is not obligatory upon him, because the default is the exoneration of responsibility. And whoever has confirmed the obligation of zakat and paid it, then forgot the time of obligation in the following year, he must pay it at the time he most likely believes coincides with the time of obligation.