To make a example as brazillian:

My close family is 4 people (my dad, mom, me, sister).

We have 6 lines from one carrier (we got it in a special package, we use 1 line per person + 2 backup lines for whatever we need, since those lines can call very cheap each other, one use for backup line for example is borrow it to extended family)

Also my dad has one workplace line with another carrier, and a Nextel Android.

And I had for a while a extra line to communicate cheaply with people of the same carrier, thus in total we have 9 mobile phone lines for 4 people.

Sometimes you see particularly important business people (like a CEO) here walking with 4 or 5 phones on his belt (one of each carrier + 1 for strictly personal stuff)