I have just posted on your other thread ... sorry again to hear about Theo.
Alvin will be confused and lonely as he is young and used to have Theo around.
You could try local rescues to see if they have any boars, baby or adult. They will know the personalities of their piggies, especially if they are adult. Usually they help with the bonding with you.
Boars can be a problem together, especially if they hit puberty at the same age. But some of the same age live peacefully together.
I did have that problem with Shaun and Stuart, litter brothers, who had a fall out. albeit when I wasn't around. I guess it was like bullying and biting but in secret. Stuart came off worse. I had to separate them. I then had Stuart neutered and he now had two sow companions. A little while later, I had Shaun neutered and he lived with two sows, but now living with little boar, Junior.
I had father and son live very happily together.
Have a think about things. I am sure that the support and advice you get from this forum will help.
Keep us posted.