Robert Pattinson says fatherhood is "a strange experience".

The actor explained portraying a parent in the final Twilight instalment has made him realise he is growing up.

In Breaking Dawn: Part 2, his character Edward Cullen is raising half-vampire, half-human daughter Renesmee with his wife Bella.

"For Edward, he kind of just started to relax in Breaking Dawn - Part 1, and also, he's a father. I have an 11-year-old kid in this. It's completely different; he's like an adult," he told MTV News. "It's really strange, and it's kind of hitting me at this period [in my life] when I'm thinking, 'Oh, I'm not a kid anymore,' when I'm playing it, so it's a strange experience, suddenly making that transition to playing fathers of 11-year-olds. I've been playing a 17-year-old for five years."

However, playing a parent seems to have inspired Robert and his co-star and off-screen girlfriend Kristen Stewart.

It has been claimed that the couple are feeling broody from spending time with onscreen daughter Mackenzie Foy.

"They would talk about how they would raise their own children," said a set source. "Kristen would say, 'Well, I'd never do this or that.' Sometimes it would start off as a joke, but you knew they were really thinking about it."

Another source added that Kristen is especially eager to start a family with her long-term boyfriend.

The 22-year-old was spotted talking to an expecting mother at a recent wedding and was overheard saying she was looking forward to having her own family one day.

"Kristen was talking to a pregnant guest and told her that she would love to have a baby with Rob," says the source. "She thought it was so cool - at one point she touched the woman's belly to feel the baby kick."