Unlike English, Spanish possessiveadjectives agree with what ispossessed and not with the possessor.Like other adjectives, possessiveadjectives agree in number and genderwith the noun they modify.
Él trabaja con sus hijos. He works withhis sons.
Ella estudia con tus hijos. She studieswith your children.
Ellos salen con su hijo. They go out withtheir son.