I've had a number of double jointed (technical term is hypermobility) students. Some of them literally can't curve their fingers in the usual way. I don't think that's a problem, just an obstacle to work around. We looked at what they can do, and worked on refining that into a technique that they do intentionally. The thing that I found interesting about two of the best of these students (the two with the highest degree of hypermobility) is that while what their fingers were doing looked painful - and would be to a less flexible person - it caused them no pain whatsoever. To them, they were simply extending their joints until the natural mechanism stopped them from extending further.
In lessons, this meant exploring ways for them to use the joints they had to create good solid stops in the left hand and to find a striking motion in the right hand that allowed for the extra play in the system. Neither appeared to have hypermobility syndrome, which is another issue. So once they figured out what their hands could do to get a good strike and a good stop, they just worked on refining that, the same as anyone else would do with their existing "normal" technique.
One outcome of this for both of the students I mentioned is that they tended to play with collapsed fingers a lot, which meant they had to focus on technique that focused on the leverage needed to get a good solid stop with the pads. Both chose to play seated, which they said helped a lot. And both were (and still are) excellent musicians who are still out playing professionally today. Once we got past these basic concepts, we didn't give the issue too much more thought and just focused on the music like everyone else in the studio did.