Greetings,

I hope you'll doing well. I have a question: Does Royal Caribbean provide Onboard birthday celebrations? if yes then is it free or we have to pay for cake and celebrations?

What do you mean by "celebrations?"

There is always cake and ice cream on the (free) main dining room menu. If you want someone to stick a candle in a piece of cake and have the waiters sing happy birthday I can't imagine you would be charged anything (or not much). If you have a travel agent, ask them. Or call Royal Caribbean. Probably someone else here knows for sure.

100% agree.

Okay Thank you

We once were on a Norwegian line cruise from NYC to Bermuda and there was a father/daughter on board celebrating a big birthday. There was also a stand from the NJ "Cake Boss" guy and she ordered a cake and they served it on Saturday night dinner to which we had been invited, so you can always check what options might be available.

Let them know about the birthday. They might decorate your room, etc.
As stated, cake and ice cream are always available, but they might sing Happy Birthday if you arrange it.

I spent my birthday on a cruise last year. There was no cake and no celebration because I didn't tell them about it. I was OK with that, so don't expect it to be automatic.