alef - mother over six of the aspirated variants of the double letters
mem - mother over six of the muted variants of the double letters and other stops (eyin, tet, qof)
shin - mother over the other sibilant letters (zeyin, samek, tsadi)
There are nine letters remaining:
רוח אלהים … נ
Two glides/semivowels: yod, vav
But, of all the letters, resh is particularly elusive, as it has traits of a guttural, a double letter, and even somewhat resembling a sibilant (when trilled), a mute/stop (when tapped), or an aspirant when rhotic.