지키고 싶다 I would like to protect and look after you
돌보고 싶다 I would like to take care of you
지키다
can be usae protect someone from adversity.
돌보다, 보살피다
It usually used when parents take care of their children or when adults take care of kids.
For couple,
소중히 여기다, 아끼다 take great care of someone, hold dear, treasure,
ex)
너를 평생 아껴 줄거야.
너를 형생 소중히 여길거야.