If team work isn't in the culture at your place it's very understandable they would react like that. If they don't see the benefits at your place and they've also only had bad experience with that at their previous places it's the natural defense mechanism.
You could do the first step for example. Put up your own stuff for early on RFC. Invite them to work collaboratively on it with you and give early feedback and see how you react. Basically: be the role model and let them follow.
Not guaranteed to work but it's one way to start some of it.
Sidenote: most teams don't actually do team work. It's a bunch of people thrown together that work on more or less loosely related stuff but everyone is out for themselves. It's a matter of the environment they have to work in in most cases. Individual metrics driven productivity culture. You can't expect someone to do good team work and collaboratively come up with the best approach when their incentives from management's side is to get as many PRs merged as they can to get that bonus and a good end year rating etc.
You could do the first step for example. Put up your own stuff for early on RFC. Invite them to work collaboratively on it with you and give early feedback and see how you react. Basically: be the role model and let them follow.
Not guaranteed to work but it's one way to start some of it.
Sidenote: most teams don't actually do team work. It's a bunch of people thrown together that work on more or less loosely related stuff but everyone is out for themselves. It's a matter of the environment they have to work in in most cases. Individual metrics driven productivity culture. You can't expect someone to do good team work and collaboratively come up with the best approach when their incentives from management's side is to get as many PRs merged as they can to get that bonus and a good end year rating etc.