Brad Pitts Play Daddy With His Twins, Knox & Vivienne in the park.

It costs Brad Pitt and Angelina Jolie a whopping $10million a year to raise their six children.

But despite the huge bills for nannies, language tutors and private jets, the youngsters prefer nothing more than spending time with their parents.

Brad treated his youngest children, twins Knox and Vivienne, to a trip to the park in Hollywood this week.

Doting dad: Brad Pitt takes his twins Knox, left, and Vivienne to the park in Hollywood

Like any proud father, Pitt took photographs of the two-year-olds on his mobile phone, coached them as they came down the slide, and kept a watchful eye as they ran around.

Both looked the spitting image of their older sister Shiloh when she was younger, as they played together.

The pair share her blonde shoulder-length hair, but while Knox has inherited his father's blue eyes, Vivienne's appeared to be her mother's dark blue/grey.

Growing up: The twins share biological sister Shiloh's blonde hair and round face

Talking of the twins Jolie has previously revealed they are 'classic boy and girl. She’s really female. And he’s really a little dude'.

From their clothes it seems their mother is right, with Vivienne choosing a girly floral dress for her day out, while Knox was dressed in shorts and a black T-shirt.

Pitt and Jolie are planing on moving their family to the south of France, where they are renovating a £35million château.

Playtime: Brad keeps a watchful eye as his son Knox tries out the slide at the playground

While the children have so far led a nomadic existence, flitting between homes around the world, their parents intend the make the château their permanent base.

Pitt's parents are to join them there, to provide a stable presence and hands on help with the children.

Perhaps they will also help cut down on the childcare bills.

As well as spending $5 million on private jets, the Hollywood pair splashed out $900,000 last year on a nanny for each of the children.

Like father like son: Knox has inherited his father's blue eyes and dress sense

Feeding Maddox, nine, Pax, seven, Zahara, six, Shiloh, four, and the twins costs around $36,000.

A source told U.S. magazine InTouch: 'They spend more than a million dollars on private tutors who travel around the world with them.

'They [even] once spent $500,000 for one stay at the Waldorf [Astoria hotel in New York].'

The couple also spent an estimated several million dollars on first-class airfare and hotel bills for the children.