从Wien-Zurich，6岁儿童是否需买卧铺票？

计划7月初一家三口去德、奥、瑞旅行，其中，从Wien-Zurich想坐火车卧铺过境。女儿6岁，但她尚不能自己独立睡一张卧铺，届时需要跟我同睡一个卧铺。所以我想请问斑竹，这种情况下，我们是需要买2张还是3张卧铺票？孩子能否跟我共用一张卧铺票而不需另行买票呢？

我看OBB上的说明如下：

Information for your journey with children

A particular advantage for our youngest:

Children until the age of 5 travel for free.

Are you planning a trip in a couchette or sleeper compartment?

If children aged up to 5 years do need an own place in a couchette or sleeper compartment, then enter these children with the age group of 6-13.

Attention: Please book in this case outward-journey and return-journey in 2 separate Booking transactions.

Are you planning a cross-border travel in the area of Austria, Germany, Switzerland?

For accompanying persons aged up to 14 years, the ÖBB-Online-Ticketing-system assumes that these are own children, grandchildren or children similar to own children. These children will be transported free of charge, only in night passenger trains is a small surcharge to pay for it. Please type in these children (from the age of 6 years) when Booking.

If you are travelling with foreign children, so please book your trip in our CallCenter 05-1717 or at our outlets.

我的理解是：

1、5岁以上且需要单独1个卧铺的则按6-13岁组订票。

2、15岁以下儿童跟父母坐OBB火车是免费的，除了夜车需要收取少量费用，需要登记6岁以上儿童信息。

我的理解正确吗？烦请能给予指引。

谢谢！