I've heard the expression "brothers of punjabi unite".

What does that mean?

In the context I heard it, I for some reason thought it was in
reference to some kind of brotherhood between Indian and Pakistani.

I'm now beginning to suspect I couldn't be more wrong and maybe is
more related to Sikh/Muslim/Hindu/Christian issues.

Hi.

You are correct that the phrase you heard has to do with brotherhood
among people in (or from) India and Pakistan.

Punjab is a region in the northern part of India and the eastern part
of Pakistan. The people of the region are of various religions
(Sikhism, Hinduism, and Islam) but are all called Punjabis and speak a
common language called Punjabi.

For more information, visit:
http://www.punjabonline.com/servlet/library.library?Action=Intro

According to the article, LINGUISTIC CLEANSING: The Sad Fate of
Punjabi in Pakistan, by Abbas Zaidi, Punjabis are divided between the
"Sikhs of East Punjab in India (who use Sanskritised script), and the
Punjabis of West Punjab in Pakistan (who use Persianised script). The
two groups cannot read or write each other's writing, but their oral
communicability is one hundred percent.
Before the partition of India in 1947 these two peoples used to live
side by side." For the full article visit:
http://www.apnaorg.com/ad/mitad.html

The article, "The 1947 Partition of India: A Paradigm for Pathological
Politics in India and Pakistan" by Ishtiaq Ahmed, discusses the long,
complicated history of Punjab since it was divided in 1947.
http://www.apnahome.net/apnaorg/article/ishtiaq.html

Many punjabis wish to promote brotherhood among people of the region,
regardless of religion. For more information, visit:
http://members.tripod.com/~ysaeed/india-pak.html

Some punjabis would even like to see the region unite politically.
Around 1995, there was quite a bit of talk on possible reunification,
as seen on these Usenet discussions:
http://groups.google.com/groups?q=punjabi%20unification&hl=en&lr=&client=googlet&sa=N&tab=wg

Google search: punjabi india pakistan
://www.google.com/search?q=punjabi+india+pakistan&btnG=Google+Search&hl=en&lr=&client=googlet

I hope this helps.

Yes, that did it, thank you.