By Karla Rodriguez Rihanna and A$AP Rocky’s firstborn son RZA is already two years old. The parents of two celebrated their child’s birthday at a party along with friends and family over the weekend, and on Monday the rapper, 35, shared some never-before-seen photos of him and his lady, along with their two boys, to his 18.5 Instagram followers. “Happiest birthday 2 my 1st born baby boy RZA,” A$AP, whose real name is Rakim Mayers, captioned the post along with 10 photos and videos of his son and their family. The family was all smiles as they posed forsome casual photos with the birthday boy h…