Injury One piggy is biting the other on the nuts! Why?! Help please.

[Jules]

Background - Pichou is 6, Hoggle is 4. Both male. They've been together since we got Hoggle. Hoggle REALLY loves his big brother, though I think Pichou would have been happier to remain an only pig.
They live in the house in a C&C cage upstairs and spend most of the day lounging around downstairs with me , with some garden time when the weather's right.
Hoggle has occasionally tried to hump Pichou and Pichou just tells him off. When Hoggle's in that mood we separate the cage with C&C grids for a few days till Hoggle's over it. Pichou has lost muscle control in his 'poop storage pocket' so I get to clean him out so that's fun :/

Pichou has blood on his nuts, Hoggle's bitten him and badly. Pichou's not particularly happy about it but he's getting lots of treats and cuddles. When I tried to see how Hoggle would treat him, Hoggle stuffed his face under Pichou's behind and seemed happy to just sit there like that. Obviously I separated them again. I can go to the vet tomorrow and get him checked out, but why is Hoggle doing this? I couldn't find any useful info on Google. They have lived together for 4 years and this is right out of the blue. Any ideas? Hoggle is suddenly obsessed with Pichou's nuts. I thought maybe Hoggle was trying to get at the 'edible poop' Pichou's made and aiming badly??
Advice please!

 

[bpatters]

That kind of behavior is often an indication that something is wrong with the pig that's being pestered. I'd take Pichou to the vet for a thorough checkup.