I’m sorry for your loss.
You shouldn’t introduce bunnies unless both are spayed and neutered, but while you’re waiting for him to be neutered, you can spend some time swapping them between hutches/swapping litter trays or stuffed toys so that they get used to each other’s scents. This also helps them to be less territorial, and once they meet, they feel like they already know who the other bunny is, it isn’t a total stranger. You can also have their hutches in view of each other, but ensure that there is always double bars between them so that they can’t nip through the bars.
Once he’s been neutered, you’ll need to wait a month to ensure he is fully recovered, and has lost all his hormones (after a week of recovery, you can go back to swapping them during this time). Then you can introduce them for short periods in a neutral space, gradually increasing the time they spend together.
I suggest reading some other threads on this forum that are marked *bonded* so you can get a good idea of the process, and good and bad signs 