The way I did it was simple. Having "The BT Price List" I could see that "reserving a block of numbers" was free, so I applied for, and got an order confirmation for, a block of 10,000 numbers on my ISDN2 lines. I did it twice, in fact.
Obviously the order did not happen, so I complained to chairman's office, as one could, at the time, and settled for a 1,000 number block as resolution if it was a "nice" one. Initially only 30 were "live" and so paid for.
We have been plagued with wrong numbers ever since, but have some cool numbers. Later, 10 of the numbers were sold by BT to an estate agent, and so I grabbed all 990 remaining and ported out. We still get bogus calls for the estate agent on numbers they don't have!
You will have seen we have 01344 400 xxx, or a least 990 of them, on the A&A site. I personally have a block of 100 of those routed to me. Once upon a time they went to ISDN2 lines in my garage (now man cave), but now are all VoIP.
So, a long time ago I set up some direct numbers for myself and my wife at home, and my kids. Back then the kids actually had analogue phones in their bedrooms on an ISDN (Avaya/Alchemy) system. It was pretty recently that the old 5 pair analogue cabling was pulled out from the house. So, yes, from birth (mostly), my kids had direct personal phone numbers (and email addresses) assigned.
Some still use them to this day, assigned to a mobile SIM card or VoIP phone as well as ringing other mobile devices.
But today I realised I needed a 2nd level of numbering, and started assigning a number scheme within the 100 numbers I have for grand kids. Yes, I have a scheme to allow for up to 9 kids for each of my kids in the numbering plan. I am assuming that by the time I have great grand kids phone numbers will really be obsolete.
The crazy thing is that the 8 year old grandchild has a mobile phone, and a number (albeit locked down on who he can call or from which he can receive calls, or texts), and I expect my 3 year old grandchild will have the same very soon.
I must admit that such a numbering scheme is something I never imagined when I started in telecoms. But now, why not. Why not have numbering the family can understand.
Next step, email addressing schemes :-)