I am sorry Alvin is unwell and is bleeding.
This will require a veterinary exam to detemrine the precise cause. The possible issues here would be that if his teeth have overgrown, this is common in hamsters and they can grow so long they cut into the roof of the mouth or lips, this is easily remedied by having them trimmed by your vet.
The other possibility is that there is a cut or wound in the mouth, this should settle with time and sometimes the hard sharp food hamsters eat can traumatise the lips or gums.
Finally, given his age we alsways worry about nasty lumps and bumps that commonly develop in older hamsters, the average life expectancy for hamsters is about 2 years of age, I've seen them much older, but neverhteless alvin is an older hamster. So it is possible that there is a mass in his mouth.
If it is bleeding constantly then try a cool compress such as moist cold cotton wool, help to the area, to encourage the bleeding to stop.
Unfortunately though to get an accurate diagnosis a vet will need to carefully examine Alvins mouth so give them a ring to sort an appointment, they will be more than happy to see him.
Good luck and I hope this helps