Players from same franchise who would've been a great fit together

[Dr Positivity]

Bobby Jones would've been perfect as the upgraded AG beside Jokic, Price's shooting makes him a great Lebron PG. Who else?

[rrravenred]

Get the feeling Miller and Haliburton would have been a lethal backcourt given Miller's offball movement and Hali's height, vision and shooting touch. Staying in the backcourt, a Billups and Dumars combo would have been defensively nasty and offensively hard to cover.

Lebron is a bit of a cheat given the teams he played with, but him and Kareem would have been a fascinating combo, like a rich man's version of the '71 Bucks.

[penbeast0]

Russell and Garnett come to mind. Erving and Durant on the Nets. Pre-injury David Robinson and Duncan (fwiw). Jerry West and Magic.

[Dr Positivity]

Dr J in the Jefferson role beside Kidd

Tmac/Shaq works like Kobe

[kdawg32086]

Arvydas Sabonis with the late 80s/early 90s Blazers core
Damian Lillard and Brandon Roy
Bill Walton and Clyde Drexler
Kevin Durant with Payton and Kemp on the Sonics
Mark Jackson with the late 90s Knicks
Luka Doncic and prime Dirk Nowitzki
Alonzo Mourning with Steve Smith and Glen Rice in Miami
Theo Ratliff and Brian Grant
Allen Iverson and Dr. J
Magic Johnson and Shaq
Rod Strickland with the late 90s Spurs
Josh Smith and Dominique Wilkins (for the in-game dunk contest between teammates)
Jeremy Lin and John Starks

[Dr Positivity]

AI and Moses - AI misses, Moses offensive rebounds

[Colbinii]

ANT and KG

Very similar mind-set and intensity. KG gets the perimeter star he always lacked.

[Ol Roy]

Robinson and Wembanyama

[penbeast0]

Arvydas Sabonis with the late 80s/early 90s Blazers core
Damian Lillard and Brandon Roy
Bill Walton and Clyde Drexler
Kevin Durant with Payton and Kemp on the Sonics
Mark Jackson with the late 90s Knicks
Luka Doncic and prime Dirk Nowitzki
Alonzo Mourning with Steve Smith and Glen Rice in Miami
Theo Ratliff and Brian Grant
Allen Iverson and Dr. J
Magic Johnson and Shaq
Rod Strickland with the late 90s Spurs
Josh Smith and Dominique Wilkins (for the in-game dunk contest between teammates)
Jeremy Lin and John Starks

If by great fit, the OP means synergy, some of these hurt spacing and would make both players less impactful. For example, Allen Iverson and Julius Erving. Erving is better than Carmelo but it would be Iverson in Denver all over again with two guy that need to slash to the basket, neither of whom is much of a floor spacer, just taking turns in iso ball.

[Yinwest]

John Havelieck with any Celtic

[Homer38]

Wilt and Curry with the warriors

[FJS]

Any of those with Karl Malone and John Stockton:
Gobert,
Okur,
Mitchell
Markkanen
Hayward

A team of Gobert, Malone, Hayward, Mitchell, Stockton in their primes would be fantastic.
Even you can sub Stockton with Deron and would be sick.

[One_and_Done]

Peak Kawhi and Duncan, Lebron and Shaq, Penny and Dwight.