Which one is grammatically correct: “MY PARENTS’ 25th MARRIAGE ANNIVERSARY SURPRISE” Or “MY PARENT’S 25th MARRIAGE ANNIVERSARY SURPRISE”

The grammatically correct option is “MY PARENTS’ 25th MARRIAGE ANNIVERSARY SURPRISE.” The use of "parents’" with the apostrophe after the "s" indicates that the anniversary celebration is for both of your parents. On the other hand, "parent’s" would imply it is for only one parent, which does not fit the context of a couple's anniversary.