Ashlee Simpson wants another baby ''next year''.

The 34-year-old singer already has 10-year-old son Bronx with her ex-husband Pete Wentz, and four-year-old Jagger with current spouse Evan Ross, but is keen to have one more child with Evan, which she thinks will happen in 2020.

She said: ''We want another one! Jagger will take care of the next little one. I would like to have another one next year, definitely.''

And Ashlee knows her two children will be excellent siblings, as Bronx already takes good care of Jagger.

She added to Us Weekly magazine: ''He's great, he was helping Jagger put her shoes on in the car. He's so sweet.''

Meanwhile, the 'Ashlee + Evan' star previously said she had ''baby fever'' after seeing her older sister Jessica give birth to her daughter Birdie earlier this year.

She said at the time: ''I'm not pregnant, but it definitely gave me the fever a little bit. She is so cute. Little Birdie. The kids were so cute - Jessica's kids with their little baby sister.''

But Ashlee might have to take some time off before she expands her family, as she previously admitted she is finding it hard being a ''working mum''.

The 'Pieces of Me' singer said: ''Music is a career by itself, having a clothing line is a career by itself, having a shoe line is a career by itself, being a mum is a career by itself. It's definitely overwhelming.''

However, luckily, Ashlee is able to lean on her husband Evan for support.

He said: ''It's hard when both parents are working, 'cause we're trying to find a way to both be there for the kids as well as work.

''I've had to change certain schedules during my day and so now I've gotta pick up the slack and go pick Bronx up from school...which is amazing 'cause, I'm definitely the youngest dad at his school. So I look swaggy.''