I think what they were trying to say was he would need kirsty's permission to take a sample for DNA testing from Ruby. As the 'parent' Kirsty needs to consent on Ruby's behalf
however - and i am not legally trained!! - if he took Kirsty to Court now, I think he could push for a Court order to have the test done - but he is worried if he went down that route - kirsty would do a runner with the baby