Kindred

google

ref

Middle English: from kin + -red (from Old English rǣden ‘condition’), with insertion of -d- in the modern spelling through phonetic development (as in thunder ).

wiktionary

ref

From Middle English kindrede, alteration (with epenthetic d) of kinrede, cünreden(“kindred”), from Old English cynrēd, cynrǣden(“kindred, family, generation, posterity, stock, species”), from cynn(“kind, sort, quality, race, family, rank, gender”) + -rǣden(“condition, state”), equivalent to kin +‎ -red. More at kin.

etymonline

ref

kindred (n.)

c. 1200, perhaps late Old English, kinraden, "family, lineage; race, nation, tribe, people; kinsfolk, blood relations," compound of kin (q.v.) + -rede (see -red). With unetymological first -d- (17c.) probably for phonetic reasons (compare sound (n.1)) but perhaps encouraged by kind (n.). As an adjective, 1520s, from the noun.