兩個人的, 英文點寫?

"The guy" is a single person, so he should be a common friend of both Julie and Bonnie.

According to the rule (see below), it should be expressed as:
The guy is Julie and Bonnie's friend.



Compound PossessivesWhen you are showing possession with compounded nouns, the apostrophe's placement depends on whether the nouns are acting separately or together.Miguel's and Cecilia's new cars are in the parking lot.
This means that each of them has at least one new car and that their ownership is a separate matter.Miguel and Cecilia's new cars are in the parking lot.
This construction tells us that Miguel and Cecilia share ownership of these cars. The possessive (indicated by 's) belongs to the entire phrase, not just to Cecilia.Another example:Lewis and Clark's expectations were very much the same.
This construction tells us that the two gentlemen held one set of expectations in common.Lewis's and Clark's expectations were altogether different.
This means that the expectations of the two men were different (rather obvious from what the sentence says, too). We signify separate ownership by writing both of the compounded proper nouns in the possessive form.

Thank all of you helping me to solve the problem.

1) 假設 Julie 和 Bonnie 是互不相識的, 就要寫 ....is Julie's and Bonnie's friend.

2) 假使 Julie and Bonnie 是相識的, 就應寫.....is Julie and Bonnie's friend.

但就文法知識, 同意cheuk yin 的更改語法建議。

Grammar before n. showing that something belongs to somebody,The guy is Julies's and Bonnie's friend.
Adv.possively .The guy's mine! she/they said possively.
She/they has convinced herself/themselves that that guy is possessed by them.
In compound possives,the apostrophe's position determines and shows the separate or togetherness.
The guy is Julies's and Bonnies's friend (in common friend)
The guy is (Julies and Bonnies)'s friend (also in common friend)

The guy is Julie's and Bonnie's friend.
But if I were you, I would rephrase it in another way: The guy is a (common) friend of Julie and Bonnie.

首先,我諗句子中應該用guy (家伙),而o吾係gug
另外,兩句句子之中,係"The guy is Julie's and Bonnie's friend". 比較好D,因為 Julie's and Bonnie's 都係用來形容個 friend嫁!!!
Hope that I can help you>.<