Rohan and Rohit are twin brothers, but they do not look ......

Rohan and Rohit are twin brothers, but they do not look alike.
In this context, "alike" means similar in appearance. The sentence suggests that despite being twin brothers, Rohan and Rohit do not share a similar physical appearance. Therefore, "alike" is the most suitable choice to complete the sentence, conveying the idea that they lack resemblance in their looks despite their familial relationship.