Street Fighter IV series
Mel appears with his parents in the prologue, the Masters family being invited to a party hosted by Karin. He is passed out most of the time sleeping, but awakens during Ken's fight with Karin.
Street Fighter III series
A three year old Mel appears in Ken's ending, where he wishes to follow in his father's footsteps and trains with him. In said ending, he was told to hit his father with all that he's got, but due to his size the highest that he could hit him was in the crotch. 
Street Fighter V Side Story: Unexpected Guests
Ken is seen playing a video game with his son in his ending. This was Mel's very first appearance, predating Street Fighter III.
Eliza gets pregnant before the second Street Fighter tournament is announced (thus, earlier than in the games' timeline), and she and Ken soon get married. He is then born after the tournament.
In the OVA, Eliza has just found out that she's pregnant but hasn't told Ken yet. As she's getting ready to give him such good news, she is captured by C. Viper in order to lure Ryu in for Seth. In the end Ken manages to rescue her in one piece, and she tells him that he's going to be a father.
- Street Fighter V: Masters Family
- It was the first time in a while that Ryu used the hot spring water in Japan. Ken said, "There's someone I want you to meet" and designated a Japanese hot spring inn as the meeting place. "A proper hot spring inn is good once in a while." The hot water that hits the trained shoulders bursts violently as if it had fallen on the marble. "Ken is also the father of a three-year-old boy........ When you become a father、 I wonder if it's hard to go out with me and go camping in the mountains." As expected, Ryu could not help feeling the flow of time by using the hot springs in his hometown of Japan. (リュウ自身、 日本の温泉の湯につかるのはしばらくぶりのことだった。ケンが「会わせたいヤツがいる」と言って、合流場所に日本の温泉宿を指定してきたのだ。「たまにはちゃんとした温泉宿もいいな」鍛えられた肩にあたる打たせ湯が、 大理石にでも落ちたかのように激しく弾けている。「ケンも、もう3歳の男の子の父親か・・・・・・・。 父 親ともなると、俺に付き合って山籠ごもりするのも大変かな」故郷日本の温泉につかって、 さすがのリュウも時の流れを感じずにはいられなかった。) from All About Street Fighter III: The Fighting Bible, page 226
- “1 year since the battle to determine the best in the world, Alex is again searching for an unseen enemy. While on his journey, he simultaneously finds martial artists from around the world with aims of waging a fight against Gill… Fulfilling ambitions of the strongest is never ending.” (世界 の 頂点 を 決める闘い から 1 年. ま だ 見 ぬ 強敵 を 求め, ふたたび アレック ス は 旅立っ た. 時 を 同じく し て , 世界中 の 格闘家 たち も, ギル を 目指し て 闘い を くり広げる を 見つける ため に, 野望 を 果たす ため に … … 最強 を 求める旅 に , 決して終わり は ない の だ .) from ALL ABOUT Capcom Fighting Game 1987-2000
- Shadaloo Combat Research Institute: Side readers : 03 「Unexpected Guests 」(Part I）
- Shadaloo Combat Research Institute: Side readers : 03 「Unexpected Guests 」(Part II）