Uchuu no Kishi Tekkaman

Both are original 70's sci-fi series that was made by the same studio, they both also had similar characters, dynamics, and same voice actors for some roles 

Both are sci-fi shows about humans living on a soon to be dead planet Earth trying to fend off alien attacks. They are from the same era and feature a similar vibe all around, as well as similar animation. Tekkaman has more of a focus on action.