Julia Roberts fears her niece Emma Roberts is making a mistake by getting married.

The 22-year-old actress announced her engagement to her 'American Horror Story' co-star Evan Peters last week, but her auntie worries she is too young to wed.

A source told the National Enquirer magazine: ''Emma's only 22, and Julia thinks she's making a big mistake by rushing into things with Evan. Julia is sure it will only lead to pain and heartbreak. She told Emma, 'You're too young to get married. You don't know what you're doing.'''

Julia - who has been married to Daniel Moder since 2002 - came close to getting hitched when she was a similar age to Emma, but her wedding to Keifer Sutheland in 1991 was called off just days before it was set to go ahead.

Julia - who was 23 at the time - later said: ''Getting married at this time in my life would have been the biggest mistake ever.''

The 'Pretty Woman' actress was also concerned about an incident last year when Emma found herself in trouble with the police after an alleged fight with Evan in a Montreal hotel room and called a family meeting - but Emma doesn't want to listen to her.

The source added: ''Emma thought Julia was overreacting then and she thinks she's overreacting now. Emma's convinced she's doing the right thing by accepting Evan's proposal and she feels Julia should just butt out.''