Here's how we found one another:

In about 2002, my first cousin Richard Thorner, Mel's son, arrived at the Bellagio Hotel in Las Vegas. 

He was travelling with his wife, Ann, and his brother and sister-in-law, Stephen and Susan Woodcock.  After checking in, Richard's brother telephoned his room, and the hotel operator asked "Which Richard Thorner do you want, the one from Texas or the one from New Hampshire?" This was the first indication of a second Richard Thorner. Later in the day, Richard received a voicemail message stating "Hi, this is Richard Thorner from Texas.  I am wondering if we are related.  Please call me."  After exchanging a couple of more voicemails, Richard (from New Hampshire) was finally able to speak in-person with the other. 

"The only Richard Thorner I am aware of from Texas is a doctor who went to Dartmouth."  "I'm the guy," responded the other.  The two arranged to meet later that evening.  Dr. Thorner and his wife arrived (after playing poker), and Richard asked him about his family.  Both families had come through New York and were Jewish.  Dr. Thorner's grandfather was Theodore, and he had an aunt, Ruth.  Richard had a great-uncle, Theodore, who had a daughter, Ruth, but they were not the same.  Finally, Richard asked Dr. Thorner whether or not his family had changed his name.  Dr. Thorner responded in the affirmative and that name was Chshunstovsky, the same family name as Richard.  Further research was needed.

Another coincidence is that both Richards graduated Dartmouth College, Dr. Thorner in '68 and Richard in '86 (note the numeric similarity).

Richard, knowing I was interested in family history, put me in touch with Richard's father Paul.

In 2002, Paul and his wife Edith came to California to visit their daughter Nancy and invited me to come over to talk and compare notes.