your feeling is understandable.
however,
please face the reality:
mom passed away, dad should live for 5 to 15 years,
if anybody can help dad to be LESS lonely and
MORE happily, it is a BIG help to you and your big brother,
especially if you are a female, you don't understand
an old man's real need!!!
if I were you, encourage dad get married with this woman
and come to canada together, let him enjoy his life for a little while.