Mary-Kate Olsen is eager to start a family.

The 27-year-old fashion designer, who sparked speculation she is engaged after she was spotted checking out rings at the Neil Lane boutique in Los Angeles several times last month, reportedly wants to have a baby with her 44-year-old beau Olivier Sarkozy, whom she has been dating since May 2012.

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

The French banker already has two children, Julien, 12, and Margot, 10, with his ex-wife Charlotte Sarkozy, and Mary-Kate has helped him form a closer bond with them.

The insider said: ''Mary-Kate has made him a better father. She remembers all the kids' special events. She thinks he's a great dad.''

The couple began living together in a $6.25 million townhouse in New York City after just three months together.

Mary-Kate previously dated artist Nate Lowman for over two years before splitting in 2010, while Olivier, who is half-brother is Nicolas Sarkozy, former President of France, romanced actress Stella Schnabel for a year before their break-up last March.

He divorced his ex-wife in 2011.