I was curious, who are your versions of Captain (the original Agent 3), Agent 4, Agent 8, and Agent 3 (the new one)?
I'm going to start. All four of my versions are male, two are Inklings and two are Octolings, all four of them have girlfriends matching their species. Having relationships outside of the New Squidbeak Splatoon is quintessential to making sure no threats can derail their lives, oh and I need to mention that this will be really long:
Captain (the original Agent 3) has seen too much in regards to what he has been through, and although he reminisces the good old days of just being your everyday kind of Inkling just playing Turf Wars and Ranked battles, he tries to join a team, but hesitates due to his skills. After he defeated DJ Octavio once, he was able to continue to play Turf Wars and Ranked Battles, but now he got swept up into doing missions for the New Squidbeak Splatoon. Now he's the captain of the group, although, wishes to go back to the times in which he could just play the less serious versions of ink battles. His girlfriend is an orange Inkling Girl.
Agent 4 is an adventurous kind of guy who is eager for action, no wonder he was excited to join the New Squidbeak Splatoon, unlike his older brother (Captain), he is ready for action on whatever missions he is sent to, though recently, he's a security guard for Off the Hook, mainly to make sure there is no intervention with Marina's development of the Memverse, ready to stop anyone who wants to barge into the room. He also used to play Turf Wars, Ranked Battles, and Salmon Run, but stopped due to his tasks with Off the Hook. His girlfriend is a pink Inkling Girl.
Agent 8 is particularly shy after his escape from Kamabo Co.'s railway system and the defeat of Commander Tartar, it seems like he will finally get the normal life on the surface he wanted, until Off the Hook goes on tour, during which he was named Eight. After seeing his own kind Sanitized down there, he was set to help test the Memverse for Marina once the program was fully developed, however, his soul was trapped inside and could only get out by defeating Smollusk, which he did and managed to get back to the real world, though while in the Memverse, he was feeling melancholy, as if his childhood was trying to come back to him, but was failing, so he went back until he completed his Pallete. He used to play Turf Wars, Ranked Battles, and Salmon Run before the Off the Hook tour but has since stopped. His girlfriend is a pink Octoling Girl.
Agent 3 (the new one) looks for scraps alongside his Smallfry pet, unlike his distant cousin, he never faced anything from Kamabo Co., however, he still did have to fight an altered version of his kind, this is when he met Captain, who silently directed him to go into the domes, find the pieces of a contraption that would allow him to cut through the fur, having to fight Deep Cut beforehand. Once he finally made it up the rocket in which he found Craig Cuttlefish dried up, he confronted Mr. Grizz in space, and with some help from DJ Octavio, Mr. Grizz was defeated. Now Agent 3 (the new one) plays Turf Wars, Anarchy Battles, and Salmon Run while visiting both of Inkopolis' hubs while returning to Splatsville from time to time. His girlfriend is a blue Octoling Girl.