Might be more souly, like stormfathers bondsmith can put together the souls of material, nightwatcher bondsmith the souls of living things, and the sibling can fuse souls to material.
Like SFBS can reknitt stone as dalinar does in with the temple.
While a NWBS might fuse together animals? Wich could explain some of the really strange creatures on roshar.
Then TSBS would be able to fuse some thing from the cognitive realm to the materialistic realm. That would be as quoted, urithiru and oathgates, but also posibly thuderclasp.
(my first time,so I might be entirely of)