I think during 3rd Life, Ren would ask Martyn to braid his hair. For technical purposes, it's practical for battle and gets the hair out of his face. But really, Ren just wanted an excuse to be close and domestic with him. Martyn always tried his best, but he was used to having short hair and his hands shook too much. Ren would laugh it off and redo it on his own. Martyn never quite figured out how to make a good braid, not even at the end.

When Last Life came around, Martyn wasn't with Ren. And that was fine. Truly, who expected alliances made for war to last in a temporary peace? It made sense, and Martyn was off with the Southernlands. But every now and then, when he'd pass by Ren or spot him in the distance, he couldn't help but feel jealous. He always had a long, perfect braid, probably made by Lizzie, or Cleo, or Bigb. They did something Martyn never quite figured out how to do; be domestic with him. So he practiced on himself. His hair was grown out long enough that he could try to make a small braid by the front of his face if he tried, and while it was never good, it was better than he was before. He'd always take it out before anyone saw it, even when he reunited with Ren. He couldn't let anyone know he was still thinking about 3rd life, that was a weakness he wouldn't let anyone see. And when they died, Ren died with a messy braid he made by himself, and Martyn died hoping that Ren would make it.

Double Life started and he didn't see Ren. Martyn was bound to Cleo which didn't go well. But he was fine on his own, Martyn was a survivor if nothing else. Ren was bound to Bigb, and they functioned well as a pair, Martyn knew that Ren would be taken care of. Even when Bigb broke his heart, and for a moment Martyn was with Ren again, he knew Ren was better off with him than he was with Martyn. He mentioned Ren's perfect braids once. He said he didn't think Bigb knew the first thing about long hair, and Ren laughed and said he didn't, but he was trying and his attempts were better than Martyn's. Martyn laughed along and agreed that he was terrible at braiding, but he couldn't stamp out the fiery jealousy that rose from that statement. Martyn didn't get to prove Ren wrong as they had been taken out early, and he had many days without him to go.

Ren wasn't there for Limited Life. Martyn hadn't been that close with Ren in the last few series, not as close as he'd like anyway, but his absence still stung. He couldn't catch glimpses of Ren when he was wandering, nor could he visit his base and make snide little jokes about it. For the first time, Ren wasn't there at all. That didn't stop him from influencing Martyn. It was a braid, messy and small in Martyn's still short hair. Then he was thinking about Ren too much, clear to anyone when his jokes seemed to reference him more often than not. And then when he turned red, a Dogwarts flag was tied around his waist. This was the first season since 3rd Life that Martyn had thought about Ren this much. And when he won, standing with hours still on his timer and no one left but bodies, Martyn, braid in his hair, couldn't help but think how much he wanted Ren to be here to see it.