Jessica Simpson has paid tribute to her ''soulmate'' Ashlee Simpson Ross.

The 'Dukes of Hazzard' star has thrown a baby shower to celebrate the impending arrival of her nephew - Ashlee's unborn son with husband Evan Ross - and Jessica paid a glowing Instagram tribute to her sibling.

The 40-year-old singer shared a picture of herself and Ashlee with the caption: ''Celebrating the new life with my soulmate, best friend, role model, baby sis @ashleesimpsonross. This lady right here is someone we should all aspire to be... determined, hilarious, artistic, loving, soulful, wise, loyal and a champion of motherhood!!!(sic)''

And the mother-of-three praised her sister for managing to stay in shape during her pregnancy.

Jessica added: ''I keep telling her that I looked like this 2 months pregnant. When she needs a good laugh I send her pics of my 3rd pregnancy journey! I love you and I can't wait to be an auntie of 3!(sic)''

Ashlee - who also has son Bronx, 11, with former husband Pete Wentz and daughter Jagger, five, with Evan - also shared photos from the event.

She was joined by Jagger, Jessica and her daughters Maxwell and Birdie, and their mother Tina Simpson.

The 35-year-old star captioned the images: ''I'm so grateful to be with my family as we get ready for my baby boy! Not long now! Thank you @tinasimpsonofficial @whambamevents for making my baby shower so special!!!

Ashlee had announced in April that she was expecting her third child and a source revealed at the time that she and Evan had been keen to expand their brood.

The insider said: ''Ashlee has been wanting another baby for a long time. They always wanted a big family!''