If you want to create a discounted ticket for customers booking on two or more children, you can do this by creating a group ticket.
Under 'Edit Entry' and then 'Tickets & Costs' you will create a new ticket type for each sibling ticket you want to offer. Here's how to set up a sibling ticket, so the booker only selects one ticket that covers multiple children at a discounted price:
As you can see, the cost is the total cost for two children, and the group ticket option is ticked. Now all you need to do is determine how many children are covered by that ticket cost. In this example, it's two.
Here's how this looks on the booking page:
As you can see, in this example we are also offering a ticket for 3 siblings, and a single ticket for one child.
The same setup can be used for a ticket setup like 'bring a friend for free' or 'twin tickets' for example.
Sibling, twins, friend