Red Arrow, Arsenal, and Artemis are all master marksmen, and combat fighters due to the training of Green Arrow. The ties are much deeper though. Red Arrow is a clone of Arsenal, making him the son to Arsenal in some ways, but Arsenal prefers to him as a big brother. Red Arrow will go out of his way to protect Arsenal at any cost. The two both feel as though Green Arrow is their adopted father. Artemis on the other hand is the daughter of Sportsmaster, one of the main villains. Since she is Sportsmaster's daughter, she is Cheshire's sister. Cheshire is the wife to Red Arrow, thus making Artemis his sister in law. Although they had their differences at first, because Red Arrow was replaced by Artemis as Green Arrow's proteje, they eventually worked out their kinks, and are allies atleast.
Green Arrow = Arsenal, Red Arrow, and Artemis.
Kid Flash is Flash's nephew. Impulse is Flash's grandson, making Impulse and Kid Flash first cousins.
Flash = Kid Flash, Impulse.
Nightwing is Batman's adopted son. Batgirl is Nightwing's close friend. Robin is Nightwing's student.
Batman = Nightwing = Batgirl, Robin.
Wonder Girl is Wonder Woman's student and her friend's daughter.
Wonder Woman = Wonder Girl.
Miss Martian is Martian Manhunter's niece. Beast Boy is Miss Martian's adopted brother.
Martian Manhunter = Miss Martian = Beast Boy.