How do I get Sole legal custody of my children

The court will grant sole custody where joint custody is not in the child's best interest. Common grounds include:
(a) Risk to the Child: That is, where the other party is known for domestic violence or abuse, alcohol or drug addiction, criminal behaviours, serious mental health issues affecting parenting.
(b) Neglect or Abandonment: Failure to provide financial support, long absence from the child’s life, refusal to take responsibility for the child or unstable living conditions, no fixed residence or the other party has an unsafe or unsuitable home environment.
(c) Child's Wishes: i.e., where the child is mature enough, the court may consider their preference.
However, you have to prove you are the better custodian.
Show the court that you can provide stable accommodation, education and healthcare, emotional and moral guidance and a safe and supportive environment.
You also have to address access rights.
You may ask the court to: Limit the other parent's access, order supervised visitation or deny access only in extreme cases.