You said this was a pressing issue, so you may not need an answer anymore, but just in case…
Here’s how I did it.
I created three paragraph styles.
Style Name: Numbered List – Normal

This is just a basic numbered list paragraph style. Make sure that you create a new list, because you’ll need to use this same list in each of the three styles you create. (I called mine “My list”.)
In the “Number” field, I used ^#.^> which inserts an en space after the period.
Ok, now for the trickery.
I created a second paragraph style called Numbered List – Group

This paragraph style needs to be identical to your “Numbered List – Normal” (same basic character formats, font, size, color, etc.) It also used “My list” and the Mode is set to “Continue from Previous Number”. The only difference with this style is for your “Number” field, use ^# ^= (That’s your number, then a space, then an en dash, then another space.)
I created a third paragraph style called Numbered List – Invisible



As you can see, with this paragraph style, I set the font size to .1 pt, leading = 0 pt, character color = none. This is going to stack any paragraphs that use this style into an invisible pile, all on one line.
Then, in the Bullets and Numbering tab, I again used “My list”, I left the “Number” field alone… it doesn’t matter what you have here because it will all be invisible anyway… and I set the Character Style to a Character Style I created called “Invisible.” (This is what’s going to make the numbers themselves vanish.)


Ok, if you have all of those styles set up, the easiest way to work with this would be in Story Editor… because some of your lines are going to be invisible on the page.
Here’s what things are going to look like in the Story Editor:

As you can see, lines 1 and 2 use Numbered List – Normal.
On line 3, I had to fake the range by starting off the line with “5. Family”. I applied Numbered List – Group to that line.
Then, I want lines 4 and 5 to be invisible, so I applied Numbered List – Invisible to those lines.
Then, items 6 and 7 are back to normal. And I do the sequence again starting with Numbered List – Group on line 8 and Numbered List – Invisible on lines 9 through 11.
The result is exactly what you wanted:

Voila. You have a live list that has the appearance of using ranges for some of the items, when in fact it is just hiding some of the items.