stronger : I'm stronger than my little sister. - CORRECT
weaker : My little sister is weaker than me.  - CORRECT
shorter : I am shorter than my mom.  - CORRECT
younger : I am younger than my dad. - CORRECT
older : I am older than my little sister.  - CORRECT

Good job, Brian! I am happy that  you were able to construct sentences with the adjectives that I provided for you. Keep up the good work^^