The plural possessive form is hamsters'.
It is hamsters'.
hamster's
hamsters'
The possessive form of the hamster belonging to my sister is "my sister's hamster".
Something belonging to more than one hamster would be written as hamsters'. So, "We looked into the hamsters' cage at the pet shop."
The plural is relatives. The plural possessive is relatives'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is suffixes. The plural possessive is suffixes'.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.
The plural of senior is seniors. The plural possessive of seniors is seniors'
The singular possessive of "ant" is "ant's" and the plural possessive is "ants'".
The correct form is "its" for the possessive form in the plural. "Its" is used for both the singular and plural possessive forms, without an apostrophe.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The plural is briefs. The plural possessive is briefs'.