For me Bhai Amrik Singh is the most wonderful kirtania I have ever heard, above all it is the piare of the kirtan which comes through in his performances.
Dharam Singhs first jatha consisted of himself and his two brothers, Bhai Shamsher Singh and Bhai Gursharan Singh (previously named Fuman Singh) on tabla. In the 70's Gursharan Singh left the jatha and tow of Dharam Singhs sons joined - Bhai Amrik Singh and Bhai Hariqbal Singh.
Bhai Dharam Singh Ji was a very learned man and a great parcharak (preacher) he passed away in 1980
Bhai Shamsher Singh Ji formed a new jatha with Bhai Mohanpal Singh on vocals and his son on tabla, Bhai Sahib Ji passed away in the mid 80's.
Bhai Amrik Singh Ji still continues with his own jatha with his brother Bratpal Singh on dilruba/israj and his son on vocals. He currently resides in Jalandhar, Punjab.
Bhai Hariqbal Singh Ji moved to Bombay/Mumbai after his fathers death, he started his own jatha for a while and later turned to doing katha and still continues to do so.
I have a collection of the kirtan of Dharam Singh Zakhami and Jatha but I am always on the look out for some more. I know they stayed in the London and Birmingham area for some time and if anyone has their kirtan from their I would be interested to hear from you. If you would like some of their kirtan, just let me know!