The Arthur actor's paternal instincts started after he was asked to be godfather to his friend's one-year-old twins.
When asked by US TV chat Ellen DeGeneres if he and Katy, 27, are planning a family, Brand said: 'I would like one. I love those little babies in the beginning. They're so lovely in that bit. Me and Katy are godparents to two twin boys. They're called Sam and Donovan.
'At first they were boring. They were just essentially little fluid factories, generating fluids - no regard for what I was wearing.
'Now, they are interesting. They smile and look at me and wonder - I'm just observing them like I’m a scientist.'
And the 36-year-old is taking his role as a godfather seriously.
Russell, who married Perry in October 2010, added: 'I can learn from them. Me and Katy are their godparents, which means we're responsible for their spiritual growth. Should be interesting.'