I'm sorry for your loss.
This is always a difficult thing to answer because a bond comes down to compatibility, rather than age. The added issue is that he is now at the start of his teens which can give a harder time trying to bond due to hormones.
We would normally say younger, and that may still stand, but you are then going to be dealing with two teenagers together - not necessarily a problem but not necessarily straightforward either.
If you get an adult then he may not like being bossed about by a dominant youngster so the bond could fail.
Do you have a rescue centre nearby who can help you with dating him?
If so then that is the best thing you can do - they will help you and if a match doesn’t work then you would have the option to try another.
If you don’t have a rescue, then you can get a baby and then have a plan b in mind that you may need separate and have side by side cages if things turn when a new piggy becomes a teen.
The alternative is to neuter him, have the six week wait and then find a female for him. That would be a good and potentially preferable option given you’re dealing with a teen boar - a sow/boar bonding can be easier and more stable. However it depends whether he can wait for a couple of months for a new friend.
