Greetings from "Up Over". Firstly I know nothing about Frank. I do however have knowledge of a father son relationship which just might fit.
Albert Andrew Wellington Greenman was b 1857, married twice and had 9 children that I am aware of born up to 1905. One of these was Albert Henry Wellington Greenman b 1884 in Hullavington, Wiltshire, England. I do not have any note of a possible marriage for Albert Junior and he died in battle at Arras, France in 1917 during WW1.
My Greenman database currently runs to about 20,000 names ignoring the mainstream US family. If there is any other snippets you have that might help me to narrow things down then please email.