Kensington Palace announced this week that Kate, 32, was expecting her second child in the spring of next year.
And Eugenie is clearly thrilled!
She told Us Weekly: "I'm very excited! Love new members of the family!"
A source also told E! News that after the royal baby was announced, the princess was heard telling pals during a night out that she had loads to celebrate.
Eugenie is currently living in New York and working for an art auction house in Manhattan.
Back in London, poor Kate has been suffering once again from hyperemesis gravidarum, a severe form of sickness that strikes during pregnancy.
She also suffered with it during her pregnancy with Prince George, now one, and was briefly hospitalised.
Kate is being treated by doctors at Kensington Palace this time around and has been forced to pull out of two planned engagements this week: a visit to Oxford University with Prince William and the opening night of Prince Harry's Invictus Games.
Her first solo overseas tour to Malta, scheduled for 21 September, is also in doubt.
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