Answer:
a) 祖 -> 助 -> 加 -> 吸
祖 SO - ancestor
助 JO , tasu(keru), suke - help, rescue, assistance
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
吸 KYUU, su(u) - suck, inhale, smoke
b) 弦 -> 畜 -> 累 -> 紋
弦 GEN, tsuru - string, bowstring
畜 CHIKU - animal raising, domestic animal
累 RUI - involvement, trouble, accumulation
紋 MON - crest, pattern