Since my main travelling countries are Austria, Italy and France, I want to present ways to reduce prices for families. It's one thing to buy a ticket for yourself, but the prices hit differently when you need to pay three or four times that price.

In Austria, I recommend the ÖBB "Vorteilscard Family". You can buy it online for the price of €19 for an adult and its validity is one year. If the price isn't discounted (Sparschiene Ticket), the adults pay 50% while the kids travel for free. You still have to pay €3 to reserve the seats for adults when it's the case.

As a practical example, our family of two adults and a child travels for the price of one adult.

In France, you can use "Carte Avantage Adulte TGV INOUI", where it is enough to be purchased by only one of the two parents, for €49. It gives a 30% discount for you, 30% for an adult who accompanies you, and a 60% discount for kids. It also puts a cap on maximum prices that you can pay, so you should check it out before travelling to France. They also have a lot of regional solutions.

With Italy, it's simpler because there's no need to pay extra. The family options are included in the total price if you search for them in advance because they apply for a limited time (eg, no less than 15 days for FRECCIAROSSA tickets).