This is about an oddity, a random happening that occurred (oddly enough) for contemporaneous families.
Let's start with Augustus John (1878-1961), best known as a portraitist who sired children by his wife and other women. His second son (by his wife) was Caspar John (1903-1984), who went on to become First Sea Lord (1960-63), attaining the rank of Admiral of the Fleet in 1962. In the Royal Navy, First Sea Lord is the highest position that an officer can attain.
Then there is Admiral Joseph Mason Reeves (1872-1948), Commander-in-Chief, U.S. Fleet (1934-36). As his Wikipedia entry indicates, Reeves was a key figure in the development of carrier-based aviation. On a lesser note, he has been credited as the first football player to wear a protective helmet. Unlike Caspar John, Reeves did not lead a navy, but his position was that of top operational officer.
Reeves' oldest son, Joseph Mason Reeves, Jr. (1898-1973, biographical snippet here, became an artist (although he too served as a naval officer, though briefly). He trained at the University of California and, after the Great War, in Europe. Unlike Augustus John, he and his work are not well known today. Below are a few examples of his paintings I found on the Web.
Like John, Reeves seems to have done a good deal of portrait painting. The examples I found were all of women. I rate his work as adequate, but just barely.