Is them feminine

No, in English there are no masculine or feminine forms. English uses gender specific nouns or pronouns for male or female.

The personal pronoun 'them' takes the place of a plural noun (or two or more nouns) for a male, a female, a common gender noun, or neuter noun as the object of a verb or a preposition.

Examples:

When my brothers are away at college I miss them.

Betty and Veronica brought Archie with them.

My neighbors sent the flowers. I must thank them.

The books were half price so I bought both of them.