Help me find a movie

[wkaminer]

Could you help me locate this movie? I just want to get the name of a movie I saw many years ago.

This is what I remember:

Movie is from the 50's or 60's probably hollywood but with co-joined european production

Mother (divorced or widowed) has two boys one teen the other preteen

Mom meets man (divorced or widowed) who lives in Europe

They move in together I believe in Italy

The guy has a daughter (teen)

Boy teen falls in love with girl teen arousing jealousy from the preteen boy

Girl gives boy teen his first kiss "not like that, a kiss like in the movies"

there is a sailing accident due to boy and girl losing site of younger brother. I believe he dies.

Woman and man separate (I believe also)

Anyone has any clues as to what this movie could be?

Thank you