بسم الله الرحمن الرحيم
If the land which your uncle owns is extra from his primary necessities or the money and business materials which he owns its value reaches up to the nisab i.e. 612 gram and 360 milligram silver after deducting the debts then your uncle is sahib-e-nisab as per the Shariah and it is not lawful to give him zakah amount. Yes, if the daughter of your uncle is poor and eligible to receive zakah i.e. she does not own such money, jewelry etc and other things beyond her primary needs that reaches up to the nisab then you may give her zakah. But don’t give such amount in one go that she becomes sahib-e-nisab, it is makrooh to do so. After she becomes sahib-e-nisab by receiving a sufficient amount of zakah, she will not become eligible for zakah again until she spends the amount i.e. she becomes poor and eligible to receive zakah.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.