The Teen Titans get another new member thanks to Kanigher and Cardy in Teen Titans 26 (March/April 1970).
We see Speedy, Kid Flash, Wonder Girl, Lilith, Hawk and Dove go through some fairly intense "training," which looks a bit more like testing endurance than anything else. Then Mr. Jupiter gives them each a penny, and sends them off to survive in the local slum, Hell's Corner.
The penny doesn't come in very useful, but their history of fighting people does, as they take on a street gang, which is causing problems for a black teenager, Mal Duncan, and his little sister. The Titans are supposed to be pacifists now, but that doesn't seem to mean too much.
Cindy Duncan will rarely appear, but Mal, despite not having any powers, is the big introduction in the story. Mr. Jupiter wants the Titans to recruit a new member, and they decide that Mal would be the one to pick.
Mal does get to show his fighting skills in the issue, as he faces off against the leader of the bad street gang in a boxing match, and wins. He agrees to join Mr. Jupiter's training program, but remains fairly aloof from the rest of the Titans. He repeats a few times that he does not feel worthy of joining the group.
To prove to himself that he has what it takes, Mal sneaks aboard an experimental rocket one night. Lilith sees him go, but does not inform the rest of the team until after the lift-off.
The story continues in the next issue.
Mal Duncan is not a bad character, and with the whole costumeless thing going on, the fact that he has no powers doesn't come off as anything that lessens him. But it does sort of emphasize that the one and only quality Mal has that none of the others do is being black.