They're rumoured to be planning an engagement.

But for now it seems fashion designer Mary-Kate Olsen and her long-term boyfriend Olivier Sarkozy just can't keep their hands off each other.

The 27-year-old former child star and her French beau, 44, playfully smooched for the Kiss Cam feature at Madison Square Garden on Saturday, where they frequent Knicks games.

The tiny temptress and the brother of former French President Nicolas Sarkozy held hands tightly while they kissed, then playfully feigned being camera-shy.

The enviable pair was seated in the pricey courtside seats, both dressed in dark clothing.

Mary-Kate wore a sparkly black sweater with a large black scarf that overwhelmed her petite frame. She wore sunglasses, despite being inside the arena, simple earrings and just a spot of lipstick. Her blond hair was pulled back.

Sarkozy, meanshile, wore a navy v-neck sweater over a navy shirt.
The couple first debuted their relationship in May 2012, and detractors were quick to raise eyebrows over the 17-year age gap.

But the union of the lovebirds, who share his $6.25million townhouse in New York City, has endured, with speculation of an impending engagement and potential pregnancy swirling for months.
In January Mary-Kate was spotted wearing a ring on her wedding finger during a trip to Paris.

A source told USWeekly magazine: 'She'd like to get pregnant but isn't so sure about marriage.'

Mary-Kate, who made her acting debut with twin sister Ashley on Full House when they were just babies, has grown close to Sarkozy's kids. The divorced banker is father to Julien, 12, and Margot, 10, his children with ex-wife Charlotte Bernard, whom he split with in 2010 after 13 years of marriage.

The actress-tuned-business woman sparked wedding rumours when she was spotted at high-end jewelery store Neil Lane in Los Angeles back in mid-November. She has reportedly returned several times since.

According to the New York Post's Page Six, Mary-Kate has her heart set on a rock 'over five carats.'

'...she really likes cushion-cut diamonds, and all of the rings she has looked at are over 5 carats,' a source told the newspaper. 'I don't think price was an issue.'

The publication reports that Mary-Kate has several rings on hold, all with a price tag of $100,000 and over.

Mary-Kate has forgone her acting career as she and twin Ashley have turned attention to their fashion empire. The pair is ready to launch two fragrances for women called Nirvana White and Nirvana Black.

The perfumes will be released through their Elizabeth and James brand - named for their two siblings - and are set to debut in Sephora stores soon.

The new fragrance line will add to their already successful womenswear collection, The Row, for which they won Womenswear Designer of the Year, by the Council of Fashion Designers of America.

The Elizabeth and James line, is a more affordable range filled with casual pieces and has also garnered success for the company.