We recently bought a JR, He is 15 weeks old now.
He plays really well with me & my family inside & outside the house.
But when He is on my mums or dads & my knee, He will go to bite my brothers.
He seems very vicious when He does this, and recently He will go for my brothers even if they go near or try to stroke him.
I am worried about Him biting, the other day He bit my younger brother who is only 5. We don't want to get rid of him, we really want help on how to stop this.
This type of behaviour He displays is not like Him.
Please can any one help .

Hi you mentioned he plays well! I have two jrt's and sometimes if they play hard or we play hard with them they can get confused and actually bite. You need to nip this in the bud or it will continue. If he bites then you should say ow! and just walk away , no eye contact. Then restart when he has calmed down but the most important thing is that you all follow this and be consistent! Good luck! They are great dogs but do need some strict training! Where abouts are you?

When he is on your mum or dad's knee, if he snarls or even shows the whites of his eyes get your mum or dad to tap him on the back and sai 'OI!' Then take him off of their kneee and onto the floor. The touch breaks him out of nastiness by casuing a distraction and the taking off the knee decreases his dominance. This should work extremeley well.

The first would work too, but your not playing with him, you are stroking him and he cannot be aggressive at all with that.

If neither of the two statements help neuter him.

BTW how old are you?