Kate Hudson's ex-husband has filed to re-examine their custody agreement for their 13-year-old son Ryder.

Kate Hudson

Kate Hudson

Black Crowes singer Chris Robinson wants the former couple's legal arrangement scrutinised and a new set of arrangements for how they should co-parent the teenager produced as Ryder reportedly wants to spend more time with his dad.

A source told Us Weekly magazine: "Ryder is at a sensitive age and wants to be with his dad."

The rock musician applied to the California Superior Court last month and paper work seen by the DailyMail.com has revealed that at a cost of $7,500 an "evaluator" will unpick their current agreement and write up fresh recommendations.

The paperwork states: "The evaluator shall perform a child custody evaluation and issue a written report and make recommendations for use by the parents and the Court in developing a parenting plan that addresses legal custody and physical custody, including where the child shall reside and visitation orders based upon the best interests of the child."

The documents also state that Kate will foot the bill for the evaluator, who will take into consideration the pair's health, mental health records, as well as their education, employment in order to thoroughly assess them both.

The 37-year-old actress and Chris, 50, divorced in 2007 after seven years of marriage and her went on to marry Allison Bridges in 2009 and have a seven-year-old daughter, Cheyenne Genevieve, with his new wife.

Kate also shares five-year-old son Bingham with Muse frontman and ex-fiancé Matthew Bellamy, and she recently paid tribute to her firstborn - who she had aged 23 - on his 13th birthday admitting she can't believe Ryder is now a teenager.

Alongside a sweet throwback picture of the mother and son on Instagram, Kate - whose mother is Goldie Hawn - wrote: "Thirteen years ... Today I reflect on how lucky I am to have spent my entire adult years being Ryder's mother. My dear Ryd man! Today you are 13! Hard to believe but I'm staring right at you and my goodness yes you are a teenager!"