filial (adj.) Look up filial at Dictionary.com
late 14c., from Middle French filial, from Late Latin filialis "of a son or daughter," from Latin filius "son," filia "daughter," possibly from a suffixed form of PIE root *bheue- "to be, exist, grow" (see be), though *dhe(i)- "to suck, suckle" (see fecund) "is more likely" [Watkins].