protective orders
If you or your children have been victims of domestic violence, you can apply for protection orders from the general civil courts according to §823.
The offender can be banned from abus and harassment by the court.
child custody
If you separate from your partner because of violence to protect yourself, you can then apply to the family court to transfer temporary sole custody. In addition the court may order that a father's Visitation Rights to stopped.
Sources
https://tkare.de/en/childrens-custody-what-are-the-rights-and-duties-of-the-parents