there is no easy way to get it done. The only way is if you're lucky enough to catch one of your neighbors online and bribe them to let your friend join it (and maybe even transfer the ownership).
On a prison server I used to play they were able to move plots but I'm not sure if that would be the same for skyblocks
I mean islands do spawn next to each other in the sense that the next person to make an island will be next to you, it used to be like that at least. So you could try being fast enough, but I do also believe it expands in multiple areas, so perhaps he/she would have to make an island 4 islands later
