‎By the Mordell‎- ‎Weil theorem‎, ‎the group of rational points on an elliptic curve over a number field is a finitely generated abelian group‎. ‎This paper studies the rank of the family E_pq:y²=x³-pqx of elliptic curves‎, ‎where p and q are distinct primes‎. ‎We give infinite families of elliptic curves of the form y²=x³-pqx with rank two‎, ‎three and four‎, ‎assuming a conjecture of Schinzel and Sierpinski is true.