Older Boyfriend

Samantha
I am 18 years old and I started dating this really awesome guy 7 months ago. Shortly after I found out that he is 26. 3 days younger than my oldest sister. I want him to meet my family but they have already decided that they don't like him 😕 is it a bad sign that he chose to date me knowing how young I am? (We are 7.5 years apart)