How to get all objects and count booleans (JS)

Let it be like this for example:

let data = {
    first: {
        surname: 'Miller',
        age: 37,
        gender: male,
        stealer: true
    },
    second: {
        surname: 'Connor',
        age: 28,
        gender: male,
        stealer: true
    },
    third: {
        surname: 'Smith',
        age: 13,
        gender: female,
        stealer: false
    }
}

How can I get everything at once and count booleans of false, without the need to manually enter each one individually?