Agree with twoin…the main acid test is time. If the child resided with the parent one day more in the year prior to the date of FAFSA filing, that parent is the custodial parent. Could your kids all stay with their dad all week this week…and then file next week?
The only time income and support come into play is if this is really an equal split in terms or residency as of the year just prior to the date of FAFSA filing.