Yep - separate them, it's the only way to be sure.
The lying on top of each other - not a concern (IMO) coz mine just see each other as convenient logs to laze upon!! lol
The 'twins' racing in front of the baby, I would see that more as 'they're hungry too', BUT, it could be them going 'get lost dweeb'.
As for the 'licking/nipping' - it could be either. But I would be separate them immediately.
And the baby will be FINE on his own and you can keep the other 3 together.
Bex
(Other bullying type things is head bobbing, puffing themselves up and leaning on an angle {making themselves look bigger}, etc etc)
