Is zakat obligatory on an amount of $700 if it is a debt owed by one's mother and brother, and if this money remains stagnant without increase or decrease, or with a decrease, knowing that the nisab in dollars is unknown?

The Zakat (definition) threshold for money is the lower value between the thresholds of gold and silver, which is currently the silver threshold (595 grams). If money reaches this threshold and a year passes, Zakat becomes obligatory on it. The mentioned amount ($700) is subject to Zakat because it has exceeded the threshold. If the money is frozen or its value decreases but does not fall below the threshold, and a year has passed, Zakat is obligatory on it. As for the money owed by the mother and brother, if the debtor is capable of repayment and not procrastinating, Zakat is due on it annually. However, if the debtor is poor or procrastinating, there is no Zakat on it until its owner collects it, at which point he pays Zakat for one year.