Question: are night elves and blood elves related?
Answer: What should be remembered is that there are only two different species of elves: kaldorei and high elves. Night elf = kaldorei, high elf = quel'dorei, blood elf = sin'dorei, and high elf = blood elf, save the name change and the eye color (which is due to the blood elves' feeding on demon magic).