Hi,
1.)Talking about my dog(which is male and I said his name already) .. I obtained IT/HIM from my uncle ... ?
For pets and animals that we have some personal attachment to, we commonly say him/her.
2.)I play with my neighbour and his dog WHICH/WHO is the twin of my dog. You could say either, based on my comment above.
I don't usually hear people use the word 'twin' for an animal.
Clive