Complex sentence: Fullerton was the second son of Admiral Sir John Fullerton and entered the Royal Navy himself in 1892 as a Cadet in HMS "Britannia" and was promoted Sub-Lieutenant in 1899 and Lieutenant in 1900.
Split into simpler sentences: Fullerton was the second son of Admiral Sir John Fullerton and entered the Royal Navy himself in 1892 as a Cadet in HMS "Britannia". He was promoted Sub-Lieutenant in 1899 and Lieutenant in 1900.