Rocky is humping a lot.

Last week we went away and left Rocky with my parents for a week. They have had dogs of their own and looked after my last Staff weekly. They also look after Rocky once a week or so although not over night and they do adore him.
They brought Rocky back home today and explained that he had been a total nightmare as he was constantly trying to dominate my mum, grabbing her arm with his paws, panting, staring and humping and he would not back down when told "NO" This was mainly in the evening when they had sat down to watch TV.
When Rocky saw me today he was as excitable as I expected and before too long he was doing the same to me as he had been to my mum. He has been relentless and any opportunity today he has been trying to hump my arms also.
He has come back a different dog to when he went. He hasn't really took any notice of the wife or kids and he follows me wherever I go and pines for me if I go out of the house. It is all a bit odd and I want him back to how he was only 7 days ago.
Has anyone else experienced this?

No sorry I haven't, very strange   

when i was in the army we got a rescue old english sheepdog,and believe it or not but he tried to hump anyone in green uniform,we took him to vets and he gave him an injection and it worked,but not sure what the injection was.

He sounds unsettled at home, this I wouldn't be too concerned about and it will probably take him a few days to settle back in.

How old is he? The humping can be for many reasons; anxiety/stress, excess energy, sexual behaviour, or learnt behaviour. If they gave him attention whenever he did this, it may have become a learnt behaviour. If he does it again, give a low key "no" response and move away, if he tries to continue put him in a time out. Biscuit humps when she's anxious or over excited and doesn't know where else to put her excess energy, it's rarely a "dominance" thing.

How old is he? Has he been neutered?!

Rocky has really calmed down today and pretty much back to himself. I guess it was some sort of separation anxiety that caused his odd behaviour.
He is 10 months old by the way and not neutered - something I wouldnt do unless there was no alternative.

Glad he's back to normal does sound like anxiety! Had a dog in kennels that would aggressively hump you whenever you were leaving his kennel lol! Biscuit is a spayed female and still humps due to anxiety, neteuring isn't often the fix for this behaviour, though can obviously take the edge off if it's sexual behaviour.

Sounds like missing you affected him glad he's returned to normal xx