Daisuke (black hair with the part in the middle) and Hiroshi (shaggy light brown hair) are best friends, and some of Ranma's only admitted male friends.
Even though they often cheer Ranma on, they frequently comment to each other at how tired they are of Ranma always getting the attention of all the girls.
In the beginning they (along with most of the male students at Furinkan) seemed to like Akane. Later they demanded that Ranma tell them who the Pigtailed Girl was and what his relationship with her was.
Daisuke and Hiroshi can best be compared to Ranma as Megane, Chibi, Perm and Kakugari are to Ataru Moroboshi in Urusei Yatsura or Sakamoto and Kobayashi are to Yusaku Godai in Maison Ikkoku, in that they are minor characters that make up the group of friends to the main male characters.
The Meaning Behind the Name
Daisuke can mean "brotherly affection" plus "assistance".
Hiroshi has a few meanings. "Remain peacful, expansive, abundant, ambition, or great soldier." These two were probably given these names not because of puns or for any humorous reason, but to show they are just average characters. Both names are fairly common Japanese names.
Takehito Koyasu & David Kaye
The stylish Takehito Koyasu has played bigger roles than just Ranma's sidekick, Daisuke. He's also voiced Hotohori in Fushigi Yuugi, Zechs Merquis in Gundam Wing and Aya Fujimiya in Weiss kreuz.
David Kaye is one of the most frequently heard voices in English anime work. Besides Ranma ½'s Soun Tendo he is also Gundam Wing's Treize Kushrinada, Kim Kaphwan in Fatal Fury, Master in Maison Ikkoku and Sesshomaru in Inuyasha.
Koji Tsujitani & Terry Klassen
Koji Tsujitani is another heavy hitter, but you would not guess it from his small role on Ranma ½. His roles include Miroku in Inuyasha, Yakumo Fuji in 3x3 Eyes, Kubo in Otaku no Video, Ryu in Street Fighter II V and Bernie in Gundam 0080.
Terry Klassen is another frequently heard voice in the English language industry. His previous roles include Maison Ikkoku's Sakamoto, Dragon Ball Z's Krillin, and Hatchie in Inuyasha.