Anyways, while they may both be the son of David Hyde, the difference is mostly technicality, name, age and origin. Jackson is a bit younger and doesn’t steal Garths backstory.
Eh there are a few differences in powers. Jackson has demonstrated powers over ice and Kaldur’ahms focuses more on magic. Plus it’s important to remember New Earth Kaldur’ahm also went by Jackson Hyde so it’s pretty mixed with them. Do DC writers even care about making sense of things anyways?