See after the Diploma in Engineering, a student can apply for the Lateral entry BE/BTech program. The lateral entry BE/BTech program provides admission to the the Diploma in Engineering students directly to the 2nd year of the BE/BTech course. So if your brother, wants to do the course of BE/BTech then he can apply for the Lateral entry program.

Now Government Polytechnic Mumbai is a Government affiliated polytechnic college of Maharashtra State Board of Technical Education, Mumbai. The college don't offers the course of BE/BTech in any stream.

You can check the top Government & Private Civil Engineering colleges in Mumbai by considering the link below:

https://engineering.careers360.com/colleges/list-of-be-btech-in-civil-engineering-colleges-in-mumbai

For more information regarding the BTech Lateral Entry consider the link below:

https://www.careers360.com/courses/b-tech-lateral-entry

I hope this helps. Wish you a great day!