It is prudent to record in writing any agreements involving loans from one person to another. By reducing the agreement to writing, any later disputes about whether the money was a gift or a loan are avoided. Disputes about the amount lent, whether there was interest due and the date for repayment are also avoided.
It is even more important to record a loan between close family members, by way of a Loan Agreement. Many such Loan Agreements record interest free loans which may be repayable on demand.
Loan Agreements are not expensive to prepare and can prevent misunderstandings which may have a catastrophic impact on you and your family.