Can the 10 ticket carnet in Paris be shared between family members?

Yes, you can share. The carent isn't a book, it's ten individual tickets.

As mentioned, the 10 ticket carnet is just 10 ordinary Metro tickets. But CDG and Orly will each require entirely different tickets.

Michelle, as Robert said, yes, you will need seperate tickets for Orly and CDG,, they are on the RER system that runs outside of Paris, and the carnet of single tickets( and yes, its not a book , just 10 single use tickets sold at a discount) are only good for the Metro zones 1-2( which is effectively all of central Paris so don't worry) and they can be used( and this may sound confusing) on the RER trains only within central PAris.. Anyways, so, seperate tickets for airports, Disneyland, Versailles, , and within city ,, regular metro tickets fine to share. Please remember, do NOT throw away a used metro ticket until you have exited the system completely. At any time an inspector can stop and ask to see the ticket you used, and there are on the spot fines .

Definitely find a system that works for you - keep all unused tickets in one place, used/cancelled (from previous trips) in another, and the ticket you're currently using in another, easy-to-reach place (like a pocket). The ink used to cancel your ticket can be very hard to make out, so it's really easy to mix up the tickets :-( And when Pat says "exited the system completely", she means street level! Inspectors have been known to wait on exiting metro passengers at the top of the stairs...(NOW move that used ticket to your used-ticket graveyard!). Have fun!

Can those same tickets (unused) be used on buses?

Jerry, A single t+ ticket from a carnet is good anywhere the Metro goes (some lines end in zone 3) and on the RER in zone 1 (all of central Paris). It's good for bus transfers up to 90 minutes after boarding the first bus, but you cannot transfer between bus and Metro/RER on one ticket. A single ticket is also good on the Montmartre funiculaire that goes up the hill to Sacre-Coeur.

Michelle, If any of your children are 10 or younger, you can buy a carnet reduit for them to share. It's half the price of a regular carnet (€6.35 rather than €12.70). Also, if any of your four days in Paris will include a Saturday or Sunday, you can buy one-day Ticket Jeunes passes for either Saturday or Sunday for anyone under 26. A zone 1-3 Ticket Jeunes pass costs €3.55. Versailles is in zone 4. If you go there on a Saturday or Sunday, you could buy zone 1-5 Ticket Jeunes passes (€7.10) for that day. A single ticket from anywhere in central Paris to Versailles-Rive Gauche costs €3.25 each way. For children 10 and younger the fare is €1.60. Orly is in zone 4 and CDG is in zone 5. You cannot use a Ticket Jeunes pass on the RER branch that goes to Orly or on the RER branch that goes to CDG, even if you have a zone 1-5 pass. If you post the ages of your children, I'll give you fares for Orly to your hotel and from your hotel to CDG.

Tim,
What great info. My children are 18, 17, 14, 13. Any help would be greatly appreciated. We will be arriving on a Saturday at noon and we do plan to go to Versailles on Sunday so I will look into a ticket jeune for that day.

Well one good thing is three of your children will be free at Versailles , and at many if not most museums in Paris.

The fastest way to get from Orly to central Paris is to take the Orlyval driverless shuttle train from the airport to Antony and the RER B from there, connecting to other RER lines and/or Metro lines to reach the station closest to your hotel. The combined fare for the Orlyval and the RER/Metro is €10.90. A slightly slower but cheaper route is to take the airport shuttle bus to the Pont de Rungis RER station. The fare is €2.50. Take the RER C into Paris and transfer to other RER lines and/or Metro lines as necessary. The fare is €4.00. The fare for a single ticket from anywhere in central Paris to CDG is €9.25. Be aware that the RER B line divides northeast of Paris. Be sure to get on a train that is going to CDG. When you go to Versailles, note that the RER C line divides on the west side of Paris. Trains that have the nameplate VICK go to Versailles-Rive Gauche. For a zoomable map of the Metro and RER system, go here: http://tinyurl.com/6xmvms4. Always hang onto your ticket until you exit the system.

Thank you so much Tim! You and everyone else have been a wealth of information!

You're welcome, Michelle. Have a great trip!

One more thought about the use of Carnet tickets. You don't need the ticket again to exit. You just push through the doors and exit. Thus, you can use one of your 10 Carnet tickets (they are separate and not in a book) to enter, clear the entry walkway that has sensors, hand the ticket back over the gate and re-used the same ticket. We've done that. I believe that each ticket is good for 10 entries. So you can give each person a ticket or use the same one multiple times. Works either way.

While you don't need to insert a ticket in a turnstile to exit a Metro station, it is necessary to do that to exit a RER station.

Larry , each ticket is good for one use, passing it back and reusuing it is actually illegal.
Also, one should always hold onto their ticket until they have completely left the system, out on the street as metro ticket inspectors can and do stop you at any point and can ask to see your validated ticket,, they can scan when it was used, so it can't be one from the day before ,, it has to have been validated within the last 90 minutes actually. Without that ticket they can and do have the ability to fine you on the spot. Its a good idea to develope a system where after you use a ticket you stick it in one pocket seperate from other tickets , they are so easy to get mixed up, until you are out side,, then look down at all the used tickets,, why to people miss the garbage bin!