My family dislike my partner...

So I’ve been with my partner for over a year now, however my sister brought up that she doesn’t really like him (I get the vibe that others don’t like him either). She said that he’s not very approachable and he seems like he can’t be bothered to make an effort with my family.

I can see where she’s coming from as he’s quiet with my family, but he’s different when it’s just me and him.

How do I bring this up with him? I want him to make more of an effort with my family and I want them to know how much of a good person he is, but I don’t want to hurt his feelings by telling him. Help please☹️