Playing dad! Heidi Klum and beau Martin Kristen get serious as they take the kids to gym class before hitting the shops

They might have only been dating for a few months, but it seems that Heidi Klum's new man Martin Kristen is already part of the family.
The bodyguard-turned-boyfriend seemed happy to play dad as he took Heidi's children to the gym class on Saturday before hitting the shops.
Clearly the doting boyfriend, Martin seemed completely relaxed with the little ones as he ferried them inside, proving that he's becoming a permanent family fixture.

Mommy and me: Heidi Klum and boyfriend and Martin Kristen ferry her children to gym class

Clutching some juice boxes for the kids, while Heidi held an apple, he seemed happy in his new role as surrogate dad.
Later in the day, the couple ran some errands together, stopping by Whole Foods in the posh Brentwood neighbourhood of Los Angeles, looking like they were stocking up for winter.
Showing that their relationship is no rebound and that things are getting serious, the happy couple seemed completely relaxed as they wheeled out a trolley full of brown packages including milk, fruits, vegetables and several bottles of wine.

Playing dad: Martin seems completely relaxed with Heidi's children as he plays a supportive role

Healthy appetites: Heidi Klum and bodyguard-turned-beau Martin Kristen hit Whole Foods on Saturday where they bought a trolley full of groceries

The Victoria's Secret catwalk star wore tinted sunglasses and had a pretty grin on her face as the cashier rang up their goods, while Martin stood by in his cool dark shades.
When it came time to pay, Martin produced the plastic and paid the hefty bill.
At one point, Heidi smiled broadly while acknowledging some fans through the store's window, while the burly Martin managed a brooding stare.
With her hair swept into a tousled bun, Heidi covered up warmly in a blue jumper and fur-trimmed jacket, as well as fashionably slashed jeans and comfortably chic trainers.

Food for love: Heidi flashed a happy grin at the check out counter, standing next to her cart loaded with her bagged purchases

Romance on the mind: The couple also stocked up on wine, perhaps a glass or two were in store for later

Such a gentleman: Heidi ranked second on Forbes 2011 list of 'world's top-earning models' with her $20 million, but when it came time to settle the grocery bill Martin paid

She let Martin, 45, who was dressed down in jeans, grey hooded jumper and braided leather bracelets, push the trolley back to the car.
One might assume he did the majority of loading up the vehicle too.
Heidi, who is often spotted out and about with her main squeeze and her four children, seems to have a permanent spot in the parking lot of Whole Foods.

Joyful: Heidi eats fruits and veggies every day, which certainly puts her in a great mood

Favourite haunt: Whole Foods is one of Heidi's most frequent go-to places in LA's Brentwood area

He steers the trolley! Heidi, looking casual in slashed jeans and fur-trimmed jacket, let Martin do the pushing

Of course having a houseful of youngsters tends to make the food in the refrigerator disappear as well.

Heidi seems blissfully in love with Martin, who worked for the German-born Project Runway star for four years before the relationship became romantic.
The honey-haired beauty began dating Martin last spring following her split with singer Seal, from whom she filed for divorce in April 2012.
Seal is the biological father of Heidi's sons Henry, seven, and Johan, six, and daughter, Lou, three, and the adoptive father of her daughter Leni, eight.
Despite a rocky transition, Heidi and Seal have tried to put on a brave front for the sake of their children and co-parent peacefully.

Grocery run: Heidi and Martin, with her daughters Leni and Lou in tow, visited Whole Foods on December 30 to stock up

And more shopping! Heidi and Martin loaded up on necessary items at Target on December 29, and that time with Heidi's sons, Johan, and Henry