What scheme is better for him is difficult to answer.
The
benefit of the old scheme was that it was a complicated formula that had a
lot of variables. For example, if the NRP were to boost his housing costs
(say, he remortgaged), increased his pension contributions, had travel
costs for
contact with his
kids...then all those variations would add up to a nice reduction. However,
the shared care reduction would only kick in after 104 nights ayear.
The new scheme is a simple 20% reduction of net income for 2 kids,
shared care reduction kicks in at 52 nights, if he has kids in his current
household there's a small reduction he could claim as well.
His
former partner marrying would not put him on the new scheme.
Does your brother have children with a current ptr? If so, and they were
to split and she put in a csa claim both applications would be treated
under the new scheme, permaenently, even if one application was later
withdrawn.