The twin prime conjecture states that, “there are infinitely many primes p such that p + 2 is also prime.” This conjecture is widely believed to be true, but it has yet to be proved or disproved.
p+2 = 19+2
21 is divisible by 3 and 7.
What about 23? 23 is a prime number yet when you add 2 to 23 you get 25 which is not prime?
The conjecture simply states that there are infinitely many primes where this occurs, not that it occurs at every prime.