Goraijers (Hurricanger - 2002) / Thunder Rangers (Ninja Storm - 2003)
Both brothers in both versions, both were additions to a main trio, they liked to be considered their own team. In Ninja Storm, the Thunder Rangers were more integrated and joined the team easily but in Hurricanger, they remained more to themselves. Rumors are that Disney and co. contemplated changing the gender for Navy Ranger, to make the team 'even' like they did with Yellow Rangers before to have two women, but in a some funny way it was made true in Gokaiger where Gokai Pink becomes Kuwagata Raijer and with a skirt.
Go-On Green and Go-On Black (Go-Onger - 2008) / Rangers Green and Black (RPM - 2009)
They didn't have a team name like the Goraijers, probably in anticipation for the Go-On Wings but they became part of the main team by episode 3, premiering in episode 2. In RPM, the focus was more on Ranger Black and Ranger Green was the comic relief. Dillon became Ranger Black in episode 3 and Ziggy joined in episode 4. I feel like the RPM two were more of a bromance duo, while the Go-Onger two were mostly with the five and most episodes didn't pair them togehter until the end to leave the trio alone.