Cinema Betty

Nanny By Chance is about someone who never intended being the caretaker of young children:

Father Goose(1964)

Finally, the nanny was behaving like a normal girl...

 I love Cary Grant, I just love him and I have a congenital weakness for a schlubby fix-er-upper kind of man (Peter Ustinov, Humphrey Bogart, Robert Mitchum (sometimes)...).  Here, Grant is at his schlubbiest and the hot, French schoolmistress that lands on his deserted island in the middle of WWII with her rag-tag international students is initially prim but finally more than a match for him.

Once For All Time does not by any measure feature a physicist brother living in Canada but that's not going to stop me:

I.Q. (1994)

I don't remember this movie very well but I do remember liking it a bit.  Meg Ryan has hair to kill for in it.
The tag line is 'With Einstein as Cupid what could possibly go wrong?' and that's how I imagine the slick, power-suited cinema pitch-man selling it to the producers...