Is there a photo ID required for the Oyster card?

no . . .

Can two people use it at the same time, or is it one per person?

just one, as the card tracks when you touch in and when you touch out.

each person needs to have their own oyster. It only allows one person in through the station gates, and back out at the other end of your journey . . . .

Now, two people COULD use the same oyster - but never at the same time nor while traveling together. One would have to stay home while the other went out on public transport. I'm sure that isn't what you meant

thanks.

Visitors 14 and over, but under 18, can get concessionary rates, and for these they DO need photocards.

Full-time students over 18 at registered London institutions can also get concessions, and also need photocards.

Details on how to get them at www.tfl.gov.uk