Link Jr. is the literal name for the son of Link and Jenna. The story did not continue long enough to depict him past infancy, but considering his development was messed up and extremely inaccurate to start with, he got a lot accomplished for a baby character.
Role[]
Link Jr. was conceived and born not long after Link and Jenna were married. Within a week or so of his birth, the King commissioned a Blessing Ceremony in his honor and, naturally, everyone in Hyrule turned up to look at him. It was at this Blessing Ceremony that he received the various gifts from the Sages and it is probable that his ability to do simple math at 4 months of age is due to Zelda's gift of knowledge. However, LQ never made a direct connection to this, so it often receives a lot of backlash for being a horribly inaccurate portrayal of childhood development.
Dark Lord Ariakas[]
Though likely not an intended plot device on LQ's behalf, an interesting fan theory posits the notion that the Dark Lord Ariakas could be a grown Link Jr. from the future. It is a compelling thought and certainly gives more depth to Link Jr.'s character.