Concerning himself, he has a silent and cool personality. He has the same surname as the middle school 1st Year Echizen.
Ryoga Echizen (越前 リョーガ, Echizen Ryoga) is a high school tennis player not mentioned in The Prince of Tennis, first appearing in The Prince of Tennis - The Two Samurai: The First Game (テニスの王子様 二人のサムライ The First Game,, Tenisu no Ōji-sama Futari no Samurai The First Game) and later appearing in an OVA in New York in which Ryoma spots him training.
Nanjirō Echizen brought Ryoga into the Echizen household in America because Ryoga's real mother died of an unknown cause. Ryoga's techniques are copies from Nanjirō Echizen, like Ryoma in the beginning of the series, but his Twist Serve, which he learned from Nanjirō also, has the opposite spin so instead of bouncing to the opponent's head it bounces away.
At first he said that Ryoma's tennis was awful (which was true when he was about five or so). It was shown that Ryoga's skills were far superior, but as Ryoma continued to improve, Ryoga began spending more time with him. In the flashbacks, it showed that he was rather close to Ryoma. It was revealed that Nanjirou lost custody over Ryogo to Ryoga's aunt (on his mother side presumably). Therefore, he no longer was allowed to live with the Echizens. When he left the Echizen's home, he gave Ryoma an orange with a message written on it saying that they'll meet again once they have become stronger.
As shown in The Prince of Tennis - The Two Samurai: The First Game, he was hired by the billionaire Sakurafubuki Hikomaro to play tennis for him in his gambling schemes.
In the fourth OVA, Another Story, Ryoga makes another appearance and finally after surprisingly large popularity and then despite never appearing in the manga. Ryoga was also brought into the manga by creator Konomi Takeshi in the sequel series New Prince of Tennis.
Ryoga bears a strong resemblance to Ryoma with his hazel eyes (blue eyes in the manga) and black-green hair as they are half-brothers.
Based on his height and muscular build Ryoga might be at least 3-4 years older than Ryoma. Ryoga's key features are his necklace, and his love of oranges. He is almost always shown tossing an orange. Like his younger brother Ryoma, he tends to juggle a tennis ball with his racket while walking. Ryoga is similar in height to the rest of the High Schoolers in that he is rather tall compared to the Middle Schoolers. In the U-17 Camp, Ryoga wears a hoodie under his uniform, with his jacket completely unzipped, and has his trademark necklace.
Ryoga has similar personality traits like Ryoma. He, too, is cocky and arrogant, but overcomes it by his dedication to tennis. He uses a similar catchphrase as Ryoma and Nanjiro--while theirs is "Mada mada dane," his is "Mada mada daze."
Ryoga is shown to be like a big brother to Ryoma (though their true relationship in the movie was not clear). He shows some protectiveness over Ryoma. Two instances include when he saved Ryoma from a group of thugs that tried to harm Ryoma when he was not paying attention to them (in the US - OVA only) and in the manga where he easily returned a serve from Byōdōin Hōō in the U-17 camp.
In the movie, The Prince of Tennis - The Two Samurai: The First Game, it is shown that he, like Nanjiro, is a shameless flirt.
Ryoga has a love for oranges and has been shown to even eat them without peeling them. Ryoga is almost always seen with an orange when off the court.
In the manga, Ryoga loves to tease Ryoma about the past. During training where Ryoga teaches Ryoma the Glowing Shot, Ryoga would say, "Saying Onii-san, Onii-san every two seconds. Always sticking to me like glue." However, Ryoma denied this. Ryoga believed that Ryoma used to worship him.
He taught Ryoma to hit 'Destruction’. In the end when the little brother mastered the shot, and got the seal of approval from the person in front of him, Ryoga takes him head on in a real fight.
Also, revealed in the manga, Ryoga and Ryoma were very close when they were younger. They would celebrate Halloween together, collect oranges together, and get into trouble together. When Ryoga had to leave he felt down and disappointed because he thought that he would no longer be Ryoma's older brother. This showed that Ryoga's teasing was true.
The promise he made from his heart to his little brother back then led him to the large sea!! Since he has a tendency to hide his true feelings, he seems to stand out because of his “do whatever you want” demeanor, but in his heart is always the existence of the little brother he parted with. Wider than the world, he is a mentor to Ryoma, as a big brother he sees the gap between deep affection and pride.
Playing Style and Techniques
Ryoga Echizen uses a tennis style based off of his adoptive fathers and therefore plays quite a lot like Echizen. He is Right-Handed, an All-Rounder, and is also very skilled since he was given the No.4 badge of the U-17 All-Japan team. He was accepted by the 1st stringers, who are usually very arrogant and confident about their abilities.
Ryoga was also able to easily return the serve of Byoudouin Houou, which shattered the wall around the court on the previous occasion. He can also hit the same shot as Byoudouin, though it's unknown if it is as strong.
The Twist serve(in the movie) is Ryoga's main serve. However, due to a different grip that Ryoga uses, the ball shoots away from the opponent, making it difficult to return. Ryoga uses this serve in the movie.
Ryoga uses this techique when Akutsu attacks him with lots of balls. He uses it to avoid shots or return them easily.
Glowing Shot is a powerful serve used by initially Hōō Byōdōin. It is so powerful it was capable of knocking out Tokugawa and causing a wall behind him to crack. It is shown that Ryoga is capable of using of it, returning it with ease, and taught Ryoma the shot as well.
He can magnificently manipulate ‘Destruction’ that only those who feel the super sweet spot can hit.
U-17 Stats 
Stats - No Data: Speed - ?: He's quick enough to instantaneously see through 10 shots hit at him simultaneously and avoid them. However, I believe we've yet to even see half of his true abilities.
Power - ?: Despite his appearance, he can certainly fire off some heavy shots. His physical strength should be considerably high.
Stamina - ?: With his slender and tall build, he seems to have very little to no body fat. His entire body seems to be flexible and springy muscles. His entire body seems almost completely like that of a professional athlete. There is high expectation for him in a real match.
Mental - ?: He has the facial expression of one who is constantly overflowing with self confidence. His mental strength doesn't seem to waver at all from anything. This is possibly from his extended period living abroad.
Technique - ?: Comparable with Byoudouin, it looks like he is endowed with considerable skill. However, his true abilities are currently immeasurable.
Kurobe Memo: This player that Byoudouin brought back with him has many mysterious qualities. Because he is a player that Byoudouin recognizes, it is of no question that he has massive potential behind him.