Final answer:
The British royal family changed its name to Windsor from Saxe-Coburg and Gotha in 1917 due to anti-German sentiment during World War I, aiming to maintain support among the British public.
Step-by-step explanation:
The British royal family changed its name during World War I due to anti-German sentiment. On the night of August 4, 1914, when Great Britain declared war against Germany, King George V perceived that having a German surname, Saxe-Coburg and Gotha, would affect the monarchy's standing and support amongst the British public.
Consequently, in 1917, the family name was changed to Windsor, a thoroughly British name associated with one of their residences, Windsor Castle.