A gift by a person who is just over the age of majority or who is particularly susceptible to be unduly influenced by his parent, guardian, trustee, attorney, or other person standing in a similar confidential relationship to one of such persons shall be closely scrutinized. Upon the slightest evidence of persuasion or influence, such gift shall be declared void at the instance of the donor or his legal representative and at any time within five years after the making of such gift.