As a general rule, a child under 7 years of age shall be in the custody of the mother (Art 213 of the Family Code). This is known as the maternal preference rule or tender-years-rule.
But this rule is not absolute and it has some exceptions, This includes finding compelling evidence showing the mother’s unfitness such as:
- habitual drunkenness
- drug addiction
- maltreatment of the child
- affliction with a communicable disease
See Agnes Hirsch vs. CA and Franklin Hirsch (GR No. 174485, July 11, 2007)