When families split up, which parent has custody of the children is sometimes decided by a court
For queries or issues around arrangements made about custody of children please seek legal advice (search your local Yellow pages for "Lawyers" then "Solicitors" and the resultant list indicates whether disputes concerning children are dealt with).
The social care services Children & Families Team would be concerned for the safety of children and would need to know if there are Child Protection concerns.
Relate for Young People (10 - 25) offers confidential counselling for young people whose parents, step-parents or other adult carers are separating or argue a lot.