In American English we tend to refer to the family in the singular, but we still way "I like them" rather than "I like it", because that word is impersonal.

yes, if you are showing a photo to someone, you can say ''This is my family'' for the next sentence, ''I like them'' is grammatically correct, but usually when describing family its more common to use ''I love them''. If you wanna be a little humorous, you might say ''we get along'' or ''they put up with me'' Cheers!

It depends on what you like very much, your family or the photo. If it is your family: I like them very much. If it is the photo: I like it very much.