There is this death in England:
Deaths March quarter 1956
John H Rennicks age 53 Southend
Have you got John with his parents in the 1911 census?
Added:
On another post you mention his parents die in about 1906 - are he and Robert Rennick his brother here in 1911?
a College and Boarding School in Review Fields (Kilkenny Rural, Kilkenny) John 8 and Robert 7?
The only birth I can see for a John Henry Ren* is in 1900, where did you get the birth date of 1902?
John Henry Renwick age 10 is with John and Anne(parents) in 1911, so could be the solidrock man.