<human>: Can you give me the gist of the text in a nutshell?

Hi all.

My cat is a 15-16 year old male, fixed tabby, who over the past few days has started licking and then chewing on my fingers.  

At first it's  alight, gently chew, almost more of a nibble, but it starts getting harder to the point I have to draw my hand away.

If i move my hand closer to him and fuss him (trying to move inside his range of movement) he'll kinda lunge for my hand and carry on.

He's also purring the whole time he does it.

Suplementary info:
He's rather old, he used to really lightly chew a few years ago, but he may have stopped that habit at some point while i was away at uni.

We had him fixed at a very young age.

He used to be one of three cats in my house - one is a young (say 5 year old cat). The other was his sister, who was the same age, who we recently had to have put to sleep after a few long conversations with the vet/the rest of the family.
<bot>: Old cat has started biting ym fingers while purring. Not too bad, but he'ss biting quite hard at times.