mentalblog.com: Calling on the descendants of Zvi Heikin

A reader writes from London in reference to Zvi Heikin mentioned in relationship with the story of Alter Rebbe son Moshe. Specially in reference to these quotes in the post there: mentalblog.com: Rabbi Moshe the son of RASHAZ Caught in the Thicket:

"A Russian Jewish historian Shaul Ginzburg wrote an article about this subject in 1931 in the NY Yiddish newspaper Zkukumft. In the article he quotes letters from Chabadnick Zvi Heikin (1876) as a first documented version of the Lubavitcher agaddta about mysterious wondered who was seen in Ukraine, in Ostropol and Fastov who revealed his identity before he died as R. Moshe ben Schneur Zalman of Liadi".

And also:

"In 1922 Rayatz wrote a letter to one of the descendants of Zvi Heikin. In the letter there is R. Moshe's dispute with Christian Theologians (a first mention of this by anybody). R. Moshe is then imprisoned, his cellmate suddenly dies and in the confusion R. Moshe escapes to go in the above mentioned Golus in Volyn area."

The reader from London asks: "I’m assuming that this is Zvi Heikin (also written Chaikin) ben Yoel who had a son called Yoel Meir. Yoel Meir Heikin was my great great grandfather. I know that Yoel Meir had good connections with the Chabad Rebbes (4th / 5th). Both Zvi Heikin and Yoel Meir moved to Israel. Zvi Heikin moved there in 1881 and died in 1883 (I think) while Yoel Meir made Aliyah in 1886 with the majority of his family and died in 1899. I have no other confirmed descendents of Zvi Heikin other than Yoel Meir and his descendants who made Aliyah – although we know that some members of the family remained in the Ukraine.

I’m trying to find out more about this Zvi Heikin. I’ve tried to find copies of the letters in 770 E Parkway in New York when I visited there a year ago, but found nothing. I believe that Zvi Heikin was an ancestor of mine, and I’m particularly interested in who the descendent was that received the letter from the Rayatz. If you have any more information on this I’d be grateful if you could send it to me".