John Valentine Connolly

I am searching for my brother John Valentine Connolly He was born in 1944, is about 5 foot 8 inches in height with brown hair and stocky build. If you know of his whereabouts,

John Connolly - Now aged 61
Last seen Harolds Cross Dublin Early June, 1969 - Doing Final Civil Engineering Exams UCD - Has not been seen or heard from since this time.
Destination no idea.

May have spent a summer working in Holland during summer holidays prior to his disappearance .
Interest would have been sports(golf/tennis/handball and reading. Very bright.

I would appreciate any information as I would like to make contact with him.