Jack Mercer has a multitude of voice roles in this cartoon with Popeye, young Popeye, three of his nephews and his mother.
One of the few times Popeye's nephews eat their spinach without complaint. But the audience never does meet the sibling of Popeye they presumably belong to. Nephews were also seen in Disney features, with Donald Duck and Mickey Mouse being uncles to several. It was an easy way to show a character's good family skills without having to marry them off, as the Production Code would have required back then.
Just before the turtle (and firecracker) reaches Popeye's seat, he and Olive are briefly shown holding hands under their desks.