Answer:
Hey! I think it is option 3rd. Option 3rd states :-
"R and J, together with their brothers, are attending the game."
Now first let us define what is a subject and a verb. Subject is where someone is doing an action to the verb. A verb is the thing that is expressing the action done by the subject.
Now back to the sentence, we can see that the subject is "R and J" and the verb is "attending". If we read the sentence, it does not sounds right. The correct form would be Subject-Verb-Object. Take a look at this one :-
"R and J are attending the game together with their brothers."
Subject is underlined. Verb is in bold.
Now the sentence would be correct. So the answer to your question is the 3rd option. Hope this helps, thank :) !!