Is zakat obligatory on gold that has reached the nisab and was placed by the wife's grandmother with the questioner to give to her orphaned grandchildren (4 and 5 years old), or must it reach the nisab after being divided between them?

If the woman owned gold for the two children while she was of sound mind and discretion, then the gift is valid, and they own it equally, unless she states otherwise. The guardian must pay zakat on the gold if the share of each child reaches the nisab, which is approximately eighty-five grams of pure gold, or its equivalent in other carats. However, if it does not reach the nisab, zakat is not obligatory on it.