A Woman Without Love(1952)

Original title: Una mujer sin amor

After indulging in an affair with a man (a friend of the family) she truly loves, a woman returns to her young son and husband for good, and loses contact with the man. Her husband is unaware of the affair. Twenty years later, there is news that the friend has died and left all of his money to the younger son in the family, which leads us to question this younger son's biological origin.