口+号 KOU, kuchi - mouth / GOU - number, pseudonym
刀 TOU, katana - sword
皇 KOU, OU - emperor
十+十+貝 JUU, tou, to - ten / KAI - shellfish
危 KI, abu(nai), aya(ui) - danger, dangerous
They all take the "fish" radical (魚 GYO, sakana, uo - fish) to become other characters.
鰐 GAKU, wani - crocodile
魛 tachiuo, TOU, etsu - beltfish
鰉 higai - gudgeon
鱝 FUN., BUN, ei - ray
鮠 GAI, GE, haya - minnow